Journal articles on the topic 'Substrats structurés'
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1
Lohman, Jeremy R., Ming Ma, Jerzy Osipiuk, Boguslaw Nocek, Youngchang Kim, Changsoo Chang, Marianne Cuff, et al. "Structural and evolutionary relationships of “AT-less” type I polyketide synthase ketosynthases." Proceedings of the National Academy of Sciences 112, no. 41 (September 29, 2015): 12693–98. http://dx.doi.org/10.1073/pnas.1515460112.
Abstract:
Acyltransferase (AT)-less type I polyketide synthases (PKSs) break the type I PKS paradigm. They lack the integrated AT domains within their modules and instead use a discrete AT that acts in trans, whereas a type I PKS module minimally contains AT, acyl carrier protein (ACP), and ketosynthase (KS) domains. Structures of canonical type I PKS KS-AT didomains reveal structured linkers that connect the two domains. AT-less type I PKS KSs have remnants of these linkers, which have been hypothesized to be AT docking domains. Natural products produced by AT-less type I PKSs are very complex because of an increased representation of unique modifying domains. AT-less type I PKS KSs possess substrate specificity and fall into phylogenetic clades that correlate with their substrates, whereas canonical type I PKS KSs are monophyletic. We have solved crystal structures of seven AT-less type I PKS KS domains that represent various sequence clusters, revealing insight into the large structural and subtle amino acid residue differences that lead to unique active site topologies and substrate specificities. One set of structures represents a larger group of KS domains from both canonical and AT-less type I PKSs that accept amino acid-containing substrates. One structure has a partial AT-domain, revealing the structural consequences of a type I PKS KS evolving into an AT-less type I PKS KS. These structures highlight the structural diversity within the AT-less type I PKS KS family, and most important, provide a unique opportunity to study the molecular evolution of substrate specificity within the type I PKSs.
2
Середин, П. В., А. С. Леньшин, А. В. Федюкин, И. Н. Арсентьев, А. В. Жаботинский, Д. Н. Николаев, Harald Leiste, and Monika Rinke. "Влияние разориентации подложки на состав, структурные и фотолюминесцентные свойства эпитаксиальных слоев, выращенных на GaAs(100)." Физика и техника полупроводников 52, no. 1 (2018): 118. http://dx.doi.org/10.21883/ftp.2018.01.45329.8565.
Abstract:
AbstractThe influence of the degree of misorientation and treatment of a GaAs substrate on the structural and optical characteristics of homoepitaxial GaAs/GaAs(100) structures grown by metal–organic chemicalvapor deposition is studied. From the data obtained by a series of structural and spectroscopic techniques, it is shown that the degree of deviation of the substrate from the exact orientation towards the [110] direction by an angle of up to 4° brings about stepwise growth of the GaAs film in the initial stage and a further increase in the degree of misorienration towards the [110] direction to 10° results in an increase in the number of structural defects in the epitaxial film. At the same time, the samples of homoepitaxial structures grown by metal–organic chemical-vapor deposition on GaAs(100) substrates misoriented by 4° towards the [110] direction possess the highest photoluminescence efficiency; it is ~15% higher than the corresponding quantity for structures grown on precisely oriented GaAs(100) substrates. Preliminary polishing of the GaAs substrate (removal of an oxide layer) also yields the intensification of photoluminescence emission compared to emission in the case of an unpolished substrate of the same type. For samples grown on substrates misoriented by 4°, such an increase in the photoluminescence efficiency is ~30%.
3
Park, Jooyoung, Ann M. Guggisberg, Audrey R. Odom, and Niraj H. Tolia. "Cap-domain closure enables diverse substrate recognition by the C2-type haloacid dehalogenase-like sugar phosphatasePlasmodium falciparumHAD1." Acta Crystallographica Section D Biological Crystallography 71, no. 9 (August 25, 2015): 1824–34. http://dx.doi.org/10.1107/s1399004715012067.
Abstract:
Haloacid dehalogenases (HADs) are a large enzyme superfamily of more than 500 000 members with roles in numerous metabolic pathways.Plasmodium falciparumHAD1 (PfHAD1) is a sugar phosphatase that regulates the methylerythritol phosphate (MEP) pathway for isoprenoid synthesis in malaria parasites. However, the structural determinants for diverse substrate recognition by HADs are unknown. Here, crystal structures were determined of PfHAD1 in complex with three sugar phosphates selected from a panel of diverse substrates that it utilizes. Cap-open and cap-closed conformations are observed, with cap closure facilitating substrate binding and ordering. These structural changes define the role of cap movement within the major subcategory of C2 HAD enzymes. The structures of an HAD bound to multiple substrates identifies binding and specificity-determining residues that define the structural basis for substrate recognition and catalysis within the HAD superfamily. While the substrate-binding region of the cap domain is flexible in the open conformations, this region becomes ordered and makes direct interactions with the substrate in the closed conformations. These studies further inform the structural and biochemical basis for catalysis within a large superfamily of HAD enzymes with diverse functions.
4
Sangian, Hanny F., and Arief Widjaja. "Effect of pretreatment method on structural changes of coconut coir dust." BioResources 12, no. 4 (September 13, 2017): 8030–46. http://dx.doi.org/10.15376/biores.12.4.8030-8046.
Abstract:
The pretreatment of a high lignin substrate, coconut coir dust, was studied by chemical techniques (NaOH solution, ionic liquid, and NaOH followed by ionic liquid) and by a physical method (subcritical water, SCW). Following substrate pretreatment and a washing step, structural analyses were performed by scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. It was found that all substrates pretreated by chemical methods had more amorphous structures than the untreated substrate. The XRD patterns of the chemically treated substrates shifted toward higher angles by 0.50° to 1.00°. However, the XRD peak symmetry of the SCW-treated substrate did not shift, but its crystallinity index decreased. The results revealed that lignocellulose treated with NaOH followed by ionic liquid at 120 °C for 30 min showed the greatest extent of structural transformation.
5
Hao, Yue, Elizabeth Pierce, Daniel Roe, Maho Morita, John A. McIntosh, Vinayak Agarwal, Thomas E. Cheatham, Eric W. Schmidt, and Satish K. Nair. "Molecular basis for the broad substrate selectivity of a peptide prenyltransferase." Proceedings of the National Academy of Sciences 113, no. 49 (November 21, 2016): 14037–42. http://dx.doi.org/10.1073/pnas.1609869113.
Abstract:
The cyanobactin prenyltransferases catalyze a series of known or unprecedented reactions on millions of different substrates, with no easily observable recognition motif and exquisite regioselectivity. Here we define the basis of broad substrate tolerance for the otherwise uncharacterized TruF family. We determined the structures of the Tyr-prenylating enzyme PagF, in complex with an isoprenoid donor analog and a panel of linear and macrocyclic peptide substrates. Unexpectedly, the structures reveal a truncated barrel fold, wherein binding of large peptide substrates is necessary to complete a solvent-exposed hydrophobic pocket to form the catalytically competent active site. Kinetic, mutational, chemical, and computational analyses revealed the structural basis of selectivity, showing a small motif within peptide substrates that is sufficient for recognition by the enzyme. Attaching this 2-residue motif to two random peptides results in their isoprenylation by PagF, demonstrating utility as a general biocatalytic platform for modifications on any peptide substrate.
6
Калыгина, В. М., В. И. Николаев, А. В. Алмаев, А. В. Цымбалов, В. В. Копьев, Ю. С. Петрова, И. А. Печников, and П. Н. Бутенко. "Влияние ультрафиолетового излучения и электрического поля на проводимость структур на основе alpha- и ε-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-." Физика и техника полупроводников 54, no. 10 (2020): 1035. http://dx.doi.org/10.21883/ftp.2020.10.49940.9449.
Abstract:
The influence of ultraviolet radiation and a strong electric field on the current-voltage characteristic of resistive structures based on polymorphic films of gallium oxide is studied. Both types of Ga2O3 films were obtained by the method of chloride vapor-phase epitaxy on smooth and structured sapphire substrates with orientation (0001). In the same process α-Ga2O3 films were deposited on smooth substrates, and gallium oxide films, with regular structures perpendicular to the substrate, containing alternating regions of the α- and ε-phases were deposited on patterned substrate. It’s was observed, that radiation with λ = 254 nm and strong electric transfer structures from a state with low resistance to a state with high resistance. The response time to UV radiation is 5 seconds, and the recovery time less than 1 s.
7
Tandrup, Tobias, Kristian E. H. Frandsen, Katja S. Johansen, Jean-Guy Berrin, and Leila Lo Leggio. "Recent insights into lytic polysaccharide monooxygenases (LPMOs)." Biochemical Society Transactions 46, no. 6 (October 31, 2018): 1431–47. http://dx.doi.org/10.1042/bst20170549.
Abstract:
Lytic polysaccharide monooxygenases (LPMOs) are copper enzymes discovered within the last 10 years. By degrading recalcitrant substrates oxidatively, these enzymes are major contributors to the recycling of carbon in nature and are being used in the biorefinery industry. Recently, two new families of LPMOs have been defined and structurally characterized, AA14 and AA15, sharing many of previously found structural features. However, unlike most LPMOs to date, AA14 degrades xylan in the context of complex substrates, while AA15 is particularly interesting because they expand the presence of LPMOs from the predominantly microbial to the animal kingdom. The first two neutron crystallography structures have been determined, which, together with high-resolution room temperature X-ray structures, have putatively identified oxygen species at or near the active site of LPMOs. Many recent computational and experimental studies have also investigated the mechanism of action and substrate-binding mode of LPMOs. Perhaps, the most significant recent advance is the increasing structural and biochemical evidence, suggesting that LPMOs follow different mechanistic pathways with different substrates, co-substrates and reductants, by behaving as monooxygenases or peroxygenases with molecular oxygen or hydrogen peroxide as a co-substrate, respectively.
8
Kusakizako, Tsukasa, Yoshiki Tanaka, Andrés Maturana, Christopher Hipolito, Teruo Kuroda, Ryuichiro Ishitani, Hiroaki Suga, and Osamu Nureki. "X-ray crystallographic analysis of a MATE multidrug transporter from V. cholerae." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C709. http://dx.doi.org/10.1107/s2053273314092900.
Abstract:
MATE (Multidrug And Toxic compound Extrusion) family transporters are highly conserved from Bacteria to Eukarya including human, and export a broad range of xenobiotics using either a proton or a sodium ion gradient across the membrane. Especially in bacterial pathogens, MATE transporters contribute to their multiple drug resistance (MDR). To understand how MATE transporters export various substrates such as drugs and thus how pathogens acquire MDR, structural analyses are essential. The crystal structures of several MATE transporters from pathogens have been reported. However, because of the limited resolution and the lack of drug-MATE transporters complex structures, the recognition mechanism of various substrates and the coupling mechanism of the cation influx and the drug efflux have been poorly understood. Although the high-resolution structures of MATE transporters from non-pathogenic archaeal P. furiosus (PfMATE) have been reported, PfMATE shares low sequence identity with MATE transporters from pathogens such as V. cholerae. Therefore, further findings of the structural mechanism of MDR caused by MATE transporters from pathogens have been needed. To understand the substrate recognition and transport mechanism of MATE transporters from pathogens, we determined the crystal structures of one of MATE transporters from V. cholerae (VcMATE) at 2.5-2.7 Å resolutions using in meso crystallization method. The high-resolution structures of VcMATE show two distinct conformations, as observed in the structures of PfMATE, and reveal the large movement of transmembrane helix 1 and the putative substrate-binding site. The structures suggest that the bending of transmembrane helix 1 and the sequential collapse of the putative substrate-binding site induce the release of the bound substrate. This conformational change during the substrate transport may be a common mechanism among MATE transporters from pathogens to non-pathogens.
9
Lamovec, Jelena, Vesna Jovic, Radoslav Aleksic, and Vesna Radojevic. "Micromechanical and structural properties of nickel coatings electrodeposited on two different substrates." Journal of the Serbian Chemical Society 74, no. 7 (2009): 817–31. http://dx.doi.org/10.2298/jsc0907817l.
Abstract:
Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness.
10
Gai, Pratibha L., Rahul Mitra, and Julia R. Weertman. "Structural variations in nanocrystalline nickel films." Pure and Applied Chemistry 74, no. 9 (January 1, 2002): 1519–26. http://dx.doi.org/10.1351/pac200274091519.
Abstract:
Nanocrystalline nickel films of technological importance have been grown on various liquid nitrogen-cooled substrates by magnetron sputtering with and without a substrate bias. The atomic structural and chemical studies have unveiled variations in inter- and intragranular structures under the different process conditions. The origin and the development of the crystallization process with and without the substrate bias voltage have been inferred from the results.
11
Mamounis, Kyle J., Maria Luiza Caldas Nogueira, Daniela Priscila Marchi Salvador, Andres Andreo-Vidal, Antonio Sanchez-Amat, and Victor L. Davidson. "Structural Determinants of the Specific Activities of an L-Amino Acid Oxidase from Pseudoalteromonas luteoviolacea CPMOR-1 with Broad Substrate Specificity." Molecules 27, no. 15 (July 24, 2022): 4726. http://dx.doi.org/10.3390/molecules27154726.
Abstract:
The Pseudoalteromonas luteoviolacea strain CPMOR-1 expresses a flavin adenine dinucleotide (FAD)-dependent L-amino acid oxidase (LAAO) with broad substrate specificity. Steady-state kinetic analysis of its reactivity towards the 20 proteinogenic amino acids showed some activity to all except proline. The relative specific activity for amino acid substrates was not correlated only with Km or kcat values, since the two parameters often varied independently of each other. Variation in Km was attributed to the differential binding affinity. Variation in kcat was attributed to differential positioning of the bound substrate relative to FAD that decreased the reaction rate. A structural model of this LAAO was compared with structures of other FAD-dependent LAAOs that have different substrate specificities: an LAAO from snake venom that prefers aromatic amino acid substrates and a fungal LAAO that is specific for lysine. While the amino acid sequences of these LAAOs are not very similar, their overall structures are comparable. The differential activity towards specific amino acids was correlated with specific residues in the active sites of these LAAOs. Residues in the active site that interact with the amino and carboxyl groups attached to the α-carbon of the substrate amino acid are conserved in all of the LAAOs. Residues that interact with the side chains of the amino acid substrates show variation. This provides insight into the structural determinants of the LAAOs that dictate their different substrate preferences. These results are of interest for harnessing these enzymes for possible applications in biotechnology, such as deracemization.
12
Gilissen, Emmanuel. "Aspects of human language: Where motherese?" Behavioral and Brain Sciences 27, no. 4 (August 2004): 514. http://dx.doi.org/10.1017/s0140525x04340112.
Abstract:
Human language is a peculiar primate communication tool because of its large neocortical substrate, comparable to the structural substrates of cognitive systems. Although monkey calls and human language rely on different structures, neural substrate for human language emotional coding, prosody, and intonation is already part of nonhuman primate vocalization circuitry. Motherese could be an aspect of language at the crossing or at the origin of communicative and cognitive content.
13
Kovalev, Alexander E., Alexander E. Filippov, and Stanislav N. Gorb. "Insect wet steps: loss of fluid from insect feet adhering to a substrate." Journal of The Royal Society Interface 10, no. 78 (January 6, 2013): 20120639. http://dx.doi.org/10.1098/rsif.2012.0639.
Abstract:
Reliable attachment ability of insect adhesive pads is proposed to be due to pad secretion. It has been shown that surface roughness strongly reduces adhesion forces of insect pads. This effect has been explained by decreased contact area and rapid fluid absorption from the pad surface by rough surfaces. However, it remains unclear how the fluid flows on rough substrates having different roughness parameters and surface energy. In this paper, we numerically studied the fluid flow on rough substrates during contact formation. The results demonstrate that an increase in the density of the substrate structures leads to an increase in fluid loss from the pad: substrates with a fine roughness absorb pad fluid faster. Decreased affinity of the solid substrate to the fluid has a more remarkable effect on the fluid loss and leads to a decrease in the fluid loss. With an increase in the aspect ratio of the substrate irregularities (porosity), the fluid loss is decreased. The numerical results obtained agree well with previous observations on insects and experimental results on nanoporous substrata. The significance of the obtained results for understanding biological wet adhesives is discussed.
14
Aruan, Irfan, Hanny F. Sangian, and Adey Tanauma. "Efek Perubahan Struktur Pati Singkong Yang Dilakukan Pretreatment Dengan Larutan Ion Dan Gelombang Mikro Terhadap Produksi Gula." Jurnal MIPA 7, no. 1 (April 19, 2018): 34. http://dx.doi.org/10.35799/jm.7.1.2018.19244.
Abstract:
Penelitian ini bertujuan untuk menganalisis hubungan perubahan struktur pati singkong terhadap produksi gula sebelum dan sesudah pretreatment gelombang mikro dan larutan ion. Pretreatment gelombang mikro dilakukan dengan meradiasikan gelombang elektromagnetik daya tertentu dengan tiga durasi yang berbedat pada substrat. Pretreatment larutan ion dilakukan dengan merendam substrat dalam larutan ion dengan dua konsentrasi garam selama empat hari dan kemudian dibandingkan dengan non-pretreatment. Substrat dikarakterisasi dengan XRD, FTIR dan SEM untuk menganalisis perubahan strukturnya. Produksi. Hasil karakterisasi menunjukkan bahwa struktur kristal pati menjadi lebih amorf dan ikatan antar molekulnya semakin lemah setelah dilakukan pretreatment. Morfologi permukaan bahan menjadi lebih kasar setelah terpapar radiasi microwave. Disisi lain, jumlah fiber pada substrat semakin berkurang setetelah direndam dalam larutan ion. Ketika substrat dihidrolisis, kandungan gula yang didapatkan lebih tinggi daripada tanpa pretreatment.This research aims to analyze the correlation of the structural change on sugar production of cassava starch before and after microwave and ionic liquid pretreatments. A microwave pretreatment was carried out by radiating electromagnetic wave with fixed power with three different durations on the substrate. The ionic liquid pretreatment was conducted by soaking the substrate in to saline water with two salt concentrations for four days and the results were compared to non-pretreatment. Then, the substrates were measured by XRD, FTIR and SEM to analiyze the structural changes. The characterization result showed that the starch crystal structure became more amorphous and molecules bonds were weaker after pretreatment. The surface morphology was rougher after being radiated by microwave. On the other hand, the fiber contents of substrate decreased after soaked on ionic liquid. When substrate were hidrolized, the sugar obtained were higher than without pretreatment.
15
Hopwood, J. J., H. Elliott, V. J. Muller, and G. T. P. Saccone. "Diagnosis of Maroteaux—Lamy syndrome by the use of radiolabelled oligosaccharides as substrates for the determination of arylsulphatase B activity." Biochemical Journal 234, no. 3 (March 15, 1986): 507–14. http://dx.doi.org/10.1042/bj2340507.
Abstract:
The kinetic parameters (Km and V) of human arylsulphatase B (4-sulpho-N-acetylgalactosamine sulphatase) activity in cultured skin fibroblasts were determined with a variety of substrates matching structural aspects of the physiological substrates in vivo chondroitin 4-sulphate and dermatan sulphate. More structurally complex substrates, in which several aspects of the aglycone structure of the natural substrate were maintained, were desulphated up to 4400 times faster than the minimum arylsulphatase-B-specific substrate, namely the monosaccharide N-acetylgalactosamine 4-sulphate. Aglycone structures that influence substrate binding and/or enzyme activity were an adjacent-residue C-6 carboxy group and a second but internal N-acetylgalactosamine 4-sulphate residue. Arylsulphatase B activity in fibroblast homogenates assayed with O-(beta-N-acetylgalactosamine 4-sulphate)-(1→)-O-D-(beta-glucuronic acid)-(1→3)-O-D-N-acetyl[1-3H] galactosaminitol 4-sulphate derived from chondroitin 4-sulphate as substrate clearly distinguished Maroteaux-Lamy-syndrome patients from normal controls and other mucopolysaccharidosis patients. We recommend the use of the above trisaccharide substrate for both postnatal and prenatal diagnosis of Maroteaux-Lamy syndrome.
16
Low-Kam, Clotilde, and Jurgen Sygusch. "Promiscuous substrate catalysis in tagatose-bisphosphate aldolase." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C467. http://dx.doi.org/10.1107/s2053273314095321.
Abstract:
Tagatose-1,6-biphosphate (TBP) from Streptococcus pyogenes offers a fascinating opportunity to probe promiscuous substrate turnover in an enzyme. TBP aldolase can cleave, apart from its own substrate TBP, three other bisphosphorylated D-hexoses including fructose-1,6-bisphosphate (FBP). These four sugars are diastereoisomers and differ in stereochemistry at carbon 3 and at carbon 4 with respect to the configuration of their hydroxyl groups. We have determined high resolution structures of the native enzyme in complex with natural substrates, FBP and TBP, and two competitive inhibitors. Since the TBP aldolase crystals are catalytically active, covalent reaction intermediates of TBP aldolase in complex with substrates were trapped under acidic conditions to minimize turnover. High resolution structural analysis revealed a snapshot of both substrates covalently trapped in the active site as Schiff bases undergoing C-C bond cleavage. The structural data pointed to Glu164, by virtue of hydrogen bonding to the substrate C4-OH, as the active site residue responsible for the proton abstraction at the C4-OH that initiates substrate cleavage. The isosteric mutant enzyme Glu164Gln, virtually devoid of activity, supported this interpretation. The structures of the Glu164Gln mutant in complex with TBP, FBP and two competitive inhibitors were solved at high resolution and corroborated the expected C4-OH hydrogen bonding of ligands with the carboxyaminde amide of Gln164, indicating retention of catalytically competent active site architecture upon mutation. The structural studies were underpinned with pH-profile studies that support Glu164 as the residue responsible for nonspecific substrate cleavage catalytic mechanism. Furthermore the pH-profile of the Glu164Gln was significantly different from that of the native enzyme corroborating Glu164 acting as the conjugate base for proton abstraction. The enzyme thus uses the same catalytic mechanism to cleave both diastereoisomers FBP and TBP, while promiscuous substrate recognition appears to be a function of subtle differences in the active site architecture when compared to the active site of the highly specific FBP aldolase from rabbit muscle.
17
Songyang, Z., K. P. Lu, Y. T. Kwon, L. H. Tsai, O. Filhol, C. Cochet, D. A. Brickey, et al. "A structural basis for substrate specificities of protein Ser/Thr kinases: primary sequence preference of casein kinases I and II, NIMA, phosphorylase kinase, calmodulin-dependent kinase II, CDK5, and Erk1." Molecular and Cellular Biology 16, no. 11 (November 1996): 6486–93. http://dx.doi.org/10.1128/mcb.16.11.6486.
Abstract:
We have developed a method to study the primary sequence specificities of protein kinases by using an oriented degenerate peptide library. We report here the substrate specificities of eight protein Ser/Thr kinases. All of the kinases studied selected distinct optimal substrates. The identified substrate specificities of these kinases, together with known crystal structures of protein kinase A, CDK2, Erk2, twitchin, and casein kinase I, provide a structural basis for the substrate recognition of protein Ser/Thr kinases. In particular, the specific selection of amino acids at the +1 and -3 positions to the substrate serine/threonine can be rationalized on the basis of sequences of protein kinases. The identification of optimal peptide substrates of CDK5, casein kinases I and II, NIMA, calmodulin-dependent kinases, Erk1, and phosphorylase kinase makes it possible to predict the potential in vivo targets of these kinases.
18
Yio, Marcus H. N., Virginia Stovin, Jörg Werdin, and Gianni Vesuviano. "Experimental analysis of green roof substrate detention characteristics." Water Science and Technology 68, no. 7 (October 1, 2013): 1477–86. http://dx.doi.org/10.2166/wst.2013.381.
Abstract:
Green roofs may make an important contribution to urban stormwater management. Rainfall-runoff models are required to evaluate green roof responses to specific rainfall inputs. The roof's hydrological response is a function of its configuration, with the substrate – or growing media – providing both retention and detention of rainfall. The objective of the research described here is to quantify the detention effects due to green roof substrates, and to propose a suitable hydrological modelling approach. Laboratory results from experimental detention tests on green roof substrates are presented. It is shown that detention increases with substrate depth and as a result of increasing substrate organic content. Model structures based on reservoir routing are evaluated, and it is found that a one-parameter reservoir routing model coupled with a parameter that describes the delay to start of runoff best fits the observed data. Preliminary findings support the hypothesis that the reservoir routing parameter values can be defined from the substrate's physical characteristics.
19
Xiang, Yong, Khanita Karaveg, and Kelley W. Moremen. "Substrate recognition and catalysis by GH47 α-mannosidases involved in Asn-linked glycan maturation in the mammalian secretory pathway." Proceedings of the National Academy of Sciences 113, no. 49 (November 17, 2016): E7890—E7899. http://dx.doi.org/10.1073/pnas.1611213113.
Abstract:
Maturation of Asn-linked oligosaccharides in the eukaryotic secretory pathway requires the trimming of nascent glycan chains to remove all glucose and several mannose residues before extension into complex-type structures on the cell surface and secreted glycoproteins. Multiple glycoside hydrolase family 47 (GH47) α-mannosidases, including endoplasmic reticulum (ER) α-mannosidase I (ERManI) and Golgi α-mannosidase IA (GMIA), are responsible for cleavage of terminal α1,2-linked mannose residues to produce uniquely trimmed oligomannose isomers that are necessary for ER glycoprotein quality control and glycan maturation. ERManI and GMIA have similar catalytic domain structures, but each enzyme cleaves distinct residues from tribranched oligomannose glycan substrates. The structural basis for branch-specific cleavage by ERManI and GMIA was explored by replacing an essential enzyme-bound Ca2+ ion with a lanthanum (La3+) ion. This ion swap led to enzyme inactivation while retaining high-affinity substrate interactions. Cocrystallization of La3+-bound enzymes with Man9GlcNAc2 substrate analogs revealed enzyme–substrate complexes with distinct modes of glycan branch insertion into the respective enzyme active-site clefts. Both enzymes had glycan interactions that extended across the entire glycan structure, but each enzyme engaged a different glycan branch and used different sets of glycan interactions. Additional mutagenesis and time-course studies of glycan cleavage probed the structural basis of enzyme specificity. The results provide insights into the enzyme catalytic mechanisms and reveal structural snapshots of the sequential glycan cleavage events. The data also indicate that full steric access to glycan substrates determines the efficiency of mannose-trimming reactions that control the conversion to complex-type structures in mammalian cells.
20
SEDANO, FRANCISCO, MARTA FLORIDO, IOANNIS RALLIS, FREE ESPINOSA, and VASILIS GEROVASILEIOU. "Comparing sessile benthos on shallow artificial versus natural hard substrates in the Eastern Mediterranean Sea." Mediterranean Marine Science 20, no. 4 (May 3, 2019): 688. http://dx.doi.org/10.12681/mms.17897.
Abstract:
Artificial structures cover a considerable part of the Mediterranean coasts. In the Aegean Sea, most studies related to artificial structures have focused in vagile fauna on harbors and marinas but little attention has been given to the sessile biota on coastal defense structures. The aim of this work was to describe for the first time the shallow sublittoral sessile benthos on coastal defense structures in Crete (Eastern Mediterranean Sea) in order to identify potential differences in comparison to natural rocky substrates, adopting both a taxonomic and functional (i.e. macroalgal structural complexity) approach. Three shallow (1-3 m) localities were studied in the north coast and three in the south coast of the island (six localities in total). At each locality, two types of hard substrate were selected: an artificial coastal defense structure (rip-rap) and the nearest natural rocky substrates. The percent cover of sessile taxa was calculated using random points counts over photoquadrats (20 x 20 cm). The structure of the assemblage differed between artificial and natural habitats. Values of Shannon-Wiener’s diversity index and number of taxa were higher in natural substrates. In addition, cover of arborescent macroalgae was lower on artificial substrates. In conclusion, rip-raps do not function as surrogates of natural hard substrates in the study area since their shallow subtidal assemblages differ in terms of community structure, diversity and functionality. The deficient performance of such artificial structures could be attributed to the combined effects of abiotic factors and biotic processes, including substrate nature and roughness as well as differential grazing pressure.
21
Liu, Hui-Yu, Ravi Kumar, Madoka Takai, and Michael Hirtz. "Enhanced Stability of Lipid Structures by Dip-Pen Nanolithography on Block-Type MPC Copolymer." Molecules 25, no. 12 (June 15, 2020): 2768. http://dx.doi.org/10.3390/molecules25122768.
Abstract:
Biomimetic lipid membranes on solid supports have been used in a plethora of applications, including as biosensors, in research on membrane proteins or as interfaces in cell experiments. For many of these applications, structured lipid membranes, e.g., in the form of arrays with features of different functionality, are highly desired. The stability of these features on a given substrate during storage and in incubation steps is key, while at the same time the substrate ideally should also exhibit antifouling properties. Here, we describe the highly beneficial properties of a 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer for the stability of supported lipid membrane structures generated by dip-pen nanolithography with phospholipids (L-DPN). The MPC copolymer substrates allow for more stable and higher membrane stack structures in comparison to other hydrophilic substrates, like glass or silicon oxide surfaces. The structures remain highly stable under immersion in liquid and subsequent incubation and washing steps. This allows multiplexed functionalization of lipid arrays with antibodies via microchannel cantilever spotting (µCS), without the need of orthogonal binding tags for each antibody type. The combined properties of the MPC copolymer substrate demonstrate a great potential for lipid-based biomedical sensing and diagnostic platforms.
22
Yu, Jie, Jingpeng Ge, Johanna Heuveling, Erwin Schneider, and Maojun Yang. "Structural basis for substrate specificity of an amino acid ABC transporter." Proceedings of the National Academy of Sciences 112, no. 16 (April 6, 2015): 5243–48. http://dx.doi.org/10.1073/pnas.1415037112.
Abstract:
ATP-binding cassette (ABC) transporters are ubiquitous integral membrane proteins that translocate a variety of substrates, ranging from ions to macromolecules, either out of or into the cytosol (hence defined as importers or exporters, respectively). It has been demonstrated that ABC exporters and importers function through a common mechanism involving conformational switches between inward-facing and outward-facing states; however, the mechanism underlying their functions, particularly substrate recognition, remains elusive. Here we report the structures of an amino acid ABC importer Art(QN)2 from Thermoanaerobacter tengcongensis composed of homodimers each of the transmembrane domain ArtQ and the nucleotide-binding domain ArtN, either in its apo form or in complex with substrates (Arg, His) and/or ATPs. The structures reveal that the straddling of the TMDs around the twofold axis forms a substrate translocation pathway across the membrane. Interestingly, each TMD has a negatively charged pocket that together create a negatively charged internal tunnel allowing amino acids carrying positively charged groups to pass through. Our structural and functional studies provide a better understanding of how ABC transporters select and translocate their substrates.
23
Tang, Jian-Fu, Chun-Hong Huang, Ching-Yen Lin, Fu-Chi Yang, and Chi-Lung Chang. "Effects of Substrate Rotation Speed on Structure and Adhesion Properties of CrN/CrAlSiN Multilayer Coatings Prepared Using High-Power Impulse Magnetron Sputtering." Coatings 10, no. 8 (July 29, 2020): 742. http://dx.doi.org/10.3390/coatings10080742.
Abstract:
We investigated the effects of substrate rotation speed on the structural and mechanical properties of CrN/CrAlSiN multilayer coatings produced using high-power impulse magnetron sputtering (HiPIMS) on silicon and high-speed steel (HSS) substrates. Structural analysis and characterization of the multilayer coatings were performed using an X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), an electron probe microanalyzer (EPMA), and a transmission electron microscope (TEM). The thickness of the bi-layer film depended on the substrate rotation speed, as follows: 12 (1.5 rpm), 9.5 (2 rpm), 6 (3 rpm), 4 (4 rpm), and 3.2 nm (5 rpm). The results revealed that the hardness and coating–substrate adhesion strength increased inversely with the thickness of the bi-layer. TEM analysis revealed smaller columnar structures in thinner CrN/CrAlSiN multilayer coatings. The highest results for hardness (20.1 GPa), elastic modulus (336 GPa), and adhesion strength (77 N) were obtained at a substrate rotation speed of 5 rpm. We also investigated the adhesion properties of the multilayer structures and formulated a hypothesis to explain adhesion strength.
24
Melzer, Björn, Tina Steinbrecher, Robin Seidel, Oliver Kraft, Ruth Schwaiger, and Thomas Speck. "The attachment strategy of English ivy: a complex mechanism acting on several hierarchical levels." Journal of The Royal Society Interface 7, no. 50 (May 12, 2010): 1383–89. http://dx.doi.org/10.1098/rsif.2010.0140.
Abstract:
English ivy ( Hedera helix L.) is able to grow on vertical substrates such as trees, rocks and house plaster, thereby attaching so firmly to the surface that when removed by force typically whole pieces of the climbing substrate are torn off. The structural details of the attachment process are not yet entirely understood. We studied the attachment process of English ivy in detail and suggest a four-phase process to describe the attachment strategy: (i) initial physical contact, (ii) form closure of the root with the substrate, (iii) chemical adhesion, and (iv) shape changes of the root hairs and form-closure with the substrate. These four phases and their variations play an important role in the attachment to differently structured surfaces. We demonstrate that, in English ivy, different mechanisms work together to allow the plant's attachment to various climbing substrates and reveal the importance of micro-fibril orientation in the root hairs for the attachment based on structural changes at the subcellular level.
25
Zhang, Jingran, Tianqi Jia, Xiaoping Li, Junjie Yang, Zhengkai Li, Guangfeng Shi, Xinming Zhang, and Zuobin Wang. "Fabrication of nano/microstructures for SERS substrates using an electrochemical method." Beilstein Journal of Nanotechnology 11 (October 16, 2020): 1568–76. http://dx.doi.org/10.3762/bjnano.11.139.
Abstract:
Based on an electrochemical method, three-dimensional arrayed nanopore structures are machined onto a Mg surface. The structured Mg surface is coated with a thin gold (Au) film, which is used as a surface-enhanced Raman scattering (SERS) substrate. A rhodamine 6G (R6G) probe molecule is used as the detection agent for the SERS measurement. Different sizes of arrayed micro/nanostructures are fabricated by different treatment time using the electrochemical process. The topographies of these micro/nanostructures and the thickness of the Au film have an influence on the Raman intensity of the Mg substrate. Furthermore, when the thickness of Au film coating is held constant, the Raman intensity on the structured Mg substrates is about five times higher after a treatment time of 1 min when compared with other treatment times. The SERS enhancement factor ranges from 106 to 1.75 × 107 under these experimental conditions. Additionally, a 10−6 mol·L−1 solution of lysozyme was successfully detected using the Mg–Au nanopore substrates. Our low-cost method is reproducible, homogeneous, and suitable for the fabrication of SERS substrates.
26
Ma, Jinming, Hsiang-Ting Lei, Francis E. Reyes, Silvia Sanchez-Martinez, Maen F. Sarhan, Johan Hattne, and Tamir Gonen. "Structural basis for substrate binding and specificity of a sodium–alanine symporter AgcS." Proceedings of the National Academy of Sciences 116, no. 6 (January 18, 2019): 2086–90. http://dx.doi.org/10.1073/pnas.1806206116.
Abstract:
The amino acid, polyamine, and organocation (APC) superfamily is the second largest superfamily of membrane proteins forming secondary transporters that move a range of organic molecules across the cell membrane. Each transporter in the APC superfamily is specific for a unique subset of substrates, even if they possess a similar structural fold. The mechanism of substrate selectivity remains, by and large, elusive. Here, we report two crystal structures of an APC member fromMethanococcus maripaludis, the alanine or glycine:cation symporter (AgcS), withl- ord-alanine bound. Structural analysis combined with site-directed mutagenesis and functional studies inform on substrate binding, specificity, and modulation of the AgcS family and reveal key structural features that allow this transporter to accommodate glycine and alanine while excluding all other amino acids. Mutation of key residues in the substrate binding site expand the selectivity to include valine and leucine. These studies provide initial insights into substrate selectivity in AgcS symporters.
27
Prabu-Jeyabalan, Moses, Ellen A. Nalivaika, Keith Romano, and Celia A. Schiffer. "Mechanism of Substrate Recognition by Drug-Resistant Human Immunodeficiency Virus Type 1 Protease Variants Revealed by a Novel Structural Intermediate." Journal of Virology 80, no. 7 (April 1, 2006): 3607–16. http://dx.doi.org/10.1128/jvi.80.7.3607-3616.2006.
Abstract:
ABSTRACT Human immunodeficiency virus type 1 (HIV-1) protease processes and cleaves the Gag and Gag-Pol polyproteins, allowing viral maturation, and therefore is an important target for antiviral therapy. Ligand binding occurs when the flaps open, allowing access to the active site. This flexibility in flap geometry makes trapping and crystallizing structural intermediates in substrate binding challenging. In this study, we report two crystal structures of two HIV-1 protease variants bound with their corresponding nucleocapsid-p1 variant. One of the flaps in each of these structures exhibits an unusual “intermediate” conformation. Analysis of the flap-intermediate and flap-closed crystal structures reveals that the intermonomer flap movements may be asynchronous and that the flap which wraps over the P3 to P1 (P3-P1) residues of the substrate might close first. This is consistent with our hypothesis that the P3-P1 region is crucial for substrate recognition. The intermediate conformation is conserved in both the wild-type and drug-resistant variants. The structural differences between the variants are evident only when the flaps are closed. Thus, a plausible structural model for the adaptability of HIV-1 protease to recognize substrates in the presence of drug-resistant mutations has been proposed.
28
Yamaguchi, Asako, Yuri Sogabe, Satomi Fukuoka, Takuo Sakai, and Toshiji Tada. "Structures of endo-1,5-α-L-arabinanase mutants fromBacillus thermodenitrificansTS-3 in complex with arabino-oligosaccharides." Acta Crystallographica Section F Structural Biology Communications 74, no. 12 (November 26, 2018): 774–80. http://dx.doi.org/10.1107/s2053230x18015947.
Abstract:
The thermostable endo-1,5-α-L-arabinanase fromBacillus thermodenitrificansTS-3 (ABN-TS) hydrolyzes the α-1,5-L-arabinofuranoside linkages of arabinan. In this study, the crystal structures of inactive ABN-TS mutants, D27A and D147N, were determined in complex with arabino-oligosaccharides. The crystal structures revealed that ABN-TS has at least six subsites in the deep V-shaped cleft formed across one face of the propeller structure. The structural features indicate that substrate recognition is profoundly influenced by the remote subsites as well as by the subsites surrounding the active center. The `open' structure of the substrate-binding cleft of the endo-acting ABN-TS is suitable for the random binding of several sugar units in polymeric substrates.
29
Kim, Hyoun Woo, Jong Woo Lee, Jeong Whan Han, Hyung Sun Kim, Mok Soon Kim, Byung Don Yoo, and Sun Keun Hwang. "Growth of In2O3 Thin Films on Lithium Aluminum Oxide Using a Triethylindium and Oxygen Mixture." Key Engineering Materials 342-343 (July 2007): 625–28. http://dx.doi.org/10.4028/www.scientific.net/kem.342-343.625.
Abstract:
Indium oxide (In2O3) films were successfully grown on LiAlO2 substrates using the triethylindium (TEI) as a precursor in the presence of oxygen in the metalorganic chemical vapor deposition process. We have established the correlation between the substrate temperature and the structural properties. The grain structures were clearly shown on the surface of the films deposited at 350°C. The root mean square (RMS) surface roughness of the In2O3 films increased with increasing the substrate temperature. A photoluminescence measurement at room temperature exhibited a yellow-green emission band centered at 585 nm.
30
Alhasan, Sarmad Fawzi Hamza, May A. Abduljabbar, Zahraa S. Alshaikhli, Makram A. Fakhri, and Nor Azizah Parmin. "Fabrication of Solar Cell Based on Copper Oxide Nanostructures Deposited Using Reactive Pulsed Laser Deposition." Defect and Diffusion Forum 418 (August 19, 2022): 99–107. http://dx.doi.org/10.4028/p-a2b0f2.
Abstract:
The deposition of copper oxide utilizing a pulsed laser deposition technique employing a reactive pulsed laser as a deposition technique is the subject of this study. The wavelength of the pulsed lase used are 1064 nm, the pulse duration is 10 ns, the laser energy of 1000 mj with different substrate temperatures (200, 3300, and 400 oC). The influence of the substrate tampering on the morphological, structural, Photolumencence, and the electrical, and attributes of the fabricated solar cell was recorded and studied using a high purity cupper target and deposited on porous silicon substrates. When compared to a crystalline silicon surface, the results of AFM show a higher possibility of better absorption and hence lower reflection. The presented results revealed the properties of the fabricated solar cell as well as a noticeable improvement in the solar cell's efficiency, whether copper deposition was used or not. The deposited films at 1064 nm were monoclinic structures with a preference for the (111) direction, according to X-ray diffraction (XRD) examination. SEM were used to study the production of nanostructures on the substrate's surface, which led to the formation of small-sized and nanostructured films.
31
Subedi, Pradeep, Hackwon Do, Jun Hyuck Lee, and Tae-Jin Oh. "Crystal Structure and Biochemical Analysis of a Cytochrome P450 CYP101D5 from Sphingomonas echinoides." International Journal of Molecular Sciences 23, no. 21 (November 1, 2022): 13317. http://dx.doi.org/10.3390/ijms232113317.
Abstract:
Cytochrome P450 enzymes (CYPs) are heme-containing enzymes that catalyze hydroxylation with a variety of biological molecules. Despite their diverse activity and substrates, the structures of CYPs are limited to a tertiary structure that is similar across all the enzymes. It has been presumed that CYPs overcome substrate selectivity with highly flexible loops and divergent sequences around the substrate entrance region. Here, we report the newly identified CYP101D5 from Sphingomonas echinoides. CYP101D5 catalyzes the hydroxylation of β-ionone and flavonoids, including naringenin and apigenin, and causes the dehydrogenation of α-ionone. A structural investigation and comparison with other CYP101 families indicated that spatial constraints at the substrate-recognition site originate from the B/C loop. Furthermore, charge distribution at the substrate binding site may be important for substrate selectivity and the preference for CYP101D5.
32
Pham, Van Dung, Tuan Anh To, Cynthia Gagné-Thivierge, Manon Couture, Patrick Lagüe, Deqiang Yao, Marie-Ève Picard, et al. "Structural insights into the putative bacterial acetylcholinesterase ChoE and its substrate inhibition mechanism." Journal of Biological Chemistry 295, no. 26 (May 5, 2020): 8708–24. http://dx.doi.org/10.1074/jbc.ra119.011809.
Abstract:
Mammalian acetylcholinesterase (AChE) is well-studied, being important in both cholinergic brain synapses and the peripheral nervous systems and also a key drug target for many diseases. In contrast, little is known about the structures and molecular mechanism of prokaryotic acetylcholinesterases. We report here the structural and biochemical characterization of ChoE, a putative bacterial acetylcholinesterase from Pseudomonas aeruginosa. Analysis of WT and mutant strains indicated that ChoE is indispensable for P. aeruginosa growth with acetylcholine as the sole carbon and nitrogen source. The crystal structure of ChoE at 1.35 Å resolution revealed that this enzyme adopts a typical fold of the SGNH hydrolase family. Although ChoE and eukaryotic AChEs catalyze the same reaction, their overall structures bear no similarities constituting an interesting example of convergent evolution. Among Ser-38, Asp-285, and His-288 of the catalytic triad residues, only Asp-285 was not essential for ChoE activity. Combined with kinetic analyses of WT and mutant proteins, multiple crystal structures of ChoE complexed with substrates, products, or reaction intermediate revealed the structural determinants for substrate recognition, snapshots of the various catalytic steps, and the molecular basis of substrate inhibition at high substrate concentrations. Our results indicate that substrate inhibition in ChoE is due to acetate release being blocked by the binding of a substrate molecule in a nonproductive mode. Because of the distinct overall folds and significant differences of the active site between ChoE and eukaryotic AChEs, these structures will serve as a prototype for other prokaryotic acetylcholinesterases.
33
Hu, Hao, and Bayanheshig. "Exploration of a Flexible Metasurface for Strain Sensors: A Perspective from 2D Grating Fabrication to Spectral Characterization." Applied Sciences 12, no. 19 (October 5, 2022): 10007. http://dx.doi.org/10.3390/app121910007.
Abstract:
The flexible plasmonic metasurface is a novel optical device consisting of a large number of subwavelength-sized noble metal (gold, silver, etc.) structures arranged in a specific pattern on a flexible substrate. The usual method for a fabricating flexible metasurface is to build nanostructures on rigid substrates and then transfer them to flexible substrates. However, problems such as structural distortion and structural loss can occur during fabrication. To address these issues, this work improved the process to fabricate and characterize a flexible plasma 2D grating–a type of metasurface composed of gold cubelets with a thickness of 50 nm and a side length of 250 nm. First, an electron beam lithography method modified by proximity effect correction was used to fabricate nanostructures on a rigid substrate. Then, the structures were transferred by a chemical functionalization and a sacrificial layer etching method. In addition, the feasibility of using flexible plasmonic 2D gratings as strain sensors was investigated in this work through a stretching test. Experimental results show that electron beam lithography improved by correcting the proximity effect enabled the fabrication of more precisely shaped nanostructures; the chemical functionalization method significantly improved the transfer yield; and the spectroscopic analysis in the stretching test demonstrated the potential of the flexible plasmonic 2D gratings for sensing applications.
34
Bae, Seongjun, Michael Dadole Ubagan, Sook Shin, and Dong Gun Kim. "Comparison of Recruitment Patterns of Sessile Marine Invertebrates According to Substrate Characteristics." International Journal of Environmental Research and Public Health 19, no. 3 (January 19, 2022): 1083. http://dx.doi.org/10.3390/ijerph19031083.
Abstract:
A community of benthic invertebrates, including sessile adult-stage invertebrates, can negatively effect corrosion, deformation, and increased fuel consumption by attaching to artificial structures, a phenomenon known as marine biofouling. Investigating the relationship between benthic communities and artificial structures or substrates (to which the organisms attach) can help clarify the factors influencing marine biofouling. Therefore, in our study, natural (stone) and artificial (rubber, tarpaulin, and iron) substrates were installed in three harbors (Mokpo, Tongyeong, and Busan), and the structures of the communities attached to each substrate were compared. The total study period was 15 months (September 2016 to December 2017), and field surveys were performed at 3-month intervals. The three survey sites had significant differences in the structure of the sessile community present. In particular, Tongyeong was significantly different from Mokpo and Busan due to the continuous dominance of Cirripedia. When comparing natural and artificial substrate by sites, significant differences were observed in the community structure in all three surveyed sites. In Mokpo and Busan, colonial ascidians were dominant on natural substrate rather than artificial substrates; post-summer, Cirripedia coverage was higher on artificial substrates than natural substrate due to corrosion. Tongyeong showed a different pattern from that of Mokpo and Busan. After the summer, Bivalvia dominated on natural substrate over artificial substrates, affecting the differences between natural and artificial substrates. Our results demonstrate the recruitment patterns of sessile marine invertebrates according to substrate characteristics and can be used as basic information for biofouling management in marine environment.
35
Sun, Nan Hai. "Efficiency Inorganic Thin Film Solar Cells with Flexible Substrate." Applied Mechanics and Materials 217-219 (November 2012): 686–89. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.686.
Abstract:
The development of CdTe/CdS solar cells on flexible substrates is reviewed in this article. Photovoltaic structures on lightweight and flexible substrates have several advantages over the heavy glass based structures in both terrestrial and space applications. The cells mounted on flexible foil are not fragile, the requirements of the supporting structures are minimum and they can be wrapped onto any suitably oriented or curved structures. The specific power of the solar cells is an important factor in space applications and hence development of photovoltaic devices on light weight substrates is interesting. CdTe is one of the leading candidates for photovoltaic applications due to its optimum band gap for the efficient photo-conversion and robustness for industrial production with a variety of film preparation methods. Flexible solar cells with conversion efficiencies exceeding 11% have been developed on polyimide foils. The development of CdTe devices on metallic substrates is impeded due to the lack of a proper ohmic contact between CdTe and the substrate. The polymer substrate has the advantage that the devices can be prepared in both “superstrate” and “substrate” configurations.
36
Ye, Jian Min. "Efficiency Organic/Inorganic Composite Thin Film Solar Cells." Advanced Materials Research 805-806 (September 2013): 3–6. http://dx.doi.org/10.4028/www.scientific.net/amr.805-806.3.
Abstract:
The development of CdTe/CdS solar cells on flexible substrates is reviewed in this article. Photovoltaic structures on lightweight and flexible substrates have several advantages over the heavy glass based structures in both terrestrial and space applications. The cells mounted on flexible foil are not fragile, the requirements of the supporting structures are minimum and they can be wrapped onto any suitably oriented or curved structures. The specific power of the solar cells is an important factor in space applications and hence development of photovoltaic devices on light weight substrates is interesting. CdTe is one of the leading candidates for photovoltaic applications due to its optimum band gap for the efficient photo-conversion and robustness for industrial production with a variety of film preparation methods. Flexible solar cells with conversion efficiencies exceeding 11% have been developed on polyimide foils. The development of CdTe devices on metallic substrates is impeded due to the lack of a proper ohmic contact between CdTe and the substrate. The polymer substrate has the advantage that the devices can be prepared in both superstrate and substrate configurations.
37
Wu, Qian Qiong, and Xiao Ying Chang. "High Performance Flexible Solar Cells with CdTe Thin Film." Applied Mechanics and Materials 209-211 (October 2012): 1754–57. http://dx.doi.org/10.4028/www.scientific.net/amm.209-211.1754.
Abstract:
The development of CdTe/CdS solar cells on flexible substrates is reviewed in this article. Photovoltaic structures on lightweight and flexible substrates have several advantages over the heavy glass based structures in both terrestrial and space applications. The cells mounted on flexible foil are not fragile, the requirements of the supporting structures are minimum and they can be wrapped onto any suitably oriented or curved structures. The specific power of the solar cells is an important factor in space applications and hence development of photovoltaic devices on light weight substrates is interesting. CdTe is one of the leading candidates for photovoltaic applications due to its optimum band gap for the efficient photo-conversion and robustness for industrial production with a variety of film preparation methods. Flexible solar cells with conversion efficiencies exceeding 11% have been developed on polyimide foils. The development of CdTe devices on metallic substrates is impeded due to the lack of a proper ohmic contact between CdTe and the substrate. The polymer substrate has the advantage that the devices can be prepared in both “superstrate” and “substrate” configurations.
38
Zhang, Jingran, Yongda Yan, Peng Miao, and Jianxiong Cai. "Fabrication of gold-coated PDMS surfaces with arrayed triangular micro/nanopyramids for use as SERS substrates." Beilstein Journal of Nanotechnology 8 (November 1, 2017): 2271–82. http://dx.doi.org/10.3762/bjnano.8.227.
Abstract:
Using the tip-based continuous indentation process, arrays of three-dimensional pyramidal cavities have been successfully machined on a copper template and the structures were successfully transferred to a polydimethylsiloxane (PDMS) surface using a reverse nanoimprinting approach. The structured PDMS surface is coated with a thin Au film, and the final substrate is demonstrated as a surface-enhanced Raman spectroscopy (SERS) substrate. Rhodamine 6G (R6G) was used as a probe molecule in the present study to confirm the SERS measurements. Arrays of micro/nanostructures of different dimensions were formed by the overlap of pyramidal cavities with different adjacent distances using the tip-based continuous indentation process. The effects of the reverse nanoimprinting process and coating process on the final topography of the structures are studied. The experimental results show that the Raman intensity of the Au-film-coated PDMS substrate is influenced by the topography of the micro/nanostructures and by the thickness of the Au film. The Raman intensity of 1362 cm−1 R6G peak on the structured Au-film-coated PDMS substrate is about 8 times higher than the SERS tests on a commercial substrate (Q-SERS). A SERS enhancement factor ranging from 7.5 × 105 to 6 × 106 was achieved using the structured Au-film-coated PDMS surface, and it was demonstrated that the method proposed in this paper is reliable, replicable, homogeneous and low-cost for the fabrication of SERS substrates.
39
Avramenko, K. A., Nina N. Roshchina, G. P. Olkhovik, Petro S. Smertenko, and Lyudmyla V. Zavyalova. "Structural and Electro-Physical Properties of ZnO Films, Obtained by a MOCVD Method on Glass and Silicon Substrates." Solid State Phenomena 230 (June 2015): 205–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.230.205.
Abstract:
This paper reports on the ZnO film structures obtained by MOCVD method from acetylacetonate of zinc and diethyldithiocarbamate of zinc on silicon substrates at 280-320 оС substrate. The structural, emitting and transport properties of the ZnO films were examined by X-ray diffraction, Scanning electronic microscopy, Photoluminescent microscopy and Current-Voltage methods. The electrical transport mechanisms were analyzed on the base of differential and injection approaches. The ZnO/Si structure with ZnO film obtained was found to be appropriate for use in electronic devices due to their structural and electrical properties.
40
Mansurova, Svetlana, Ismael Cosme, Andrey Kosarev, Antonio J. Olivares, Carlos Ospina, and Hiram E. Martinez. "AZO/PEDOT:PSS Polymer Frontal Interface Deposited on Flexible Substrates for a-Si:H Photovoltaic Applications." Polymers 10, no. 10 (September 27, 2018): 1068. http://dx.doi.org/10.3390/polym10101068.
Abstract:
Thin-film hybrid organic-inorganic photovoltaic structures based on hydrogenated silicon (Si:H), poly(3,4ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) polymer Al-doped ZnO (AZO) films deposited on different types of flexible substrates have been fabricated and investigated. The compatibility of the polymer and inorganic materials regimes and deposition techniques used for device fabrication has been demonstrated on flexible substrates. Morphological characteristics of transparent Al-doped ZnO (AZO) films deposited on substrates have been measured by atomic force microscopy. Electronic characteristics of the fabricated photovoltaic structures have been measured and analyzed for different thicknesses of the transparent electrodes and different substrate types. Photovoltaic hybrid structure on polyethylene naphthalate (PEN) substrate showed the best characteristics: short circuit current density Jsc = 9.79 mA/cm2, open circuit voltage Uoc = 565 mV, and PCE η = 1.3%. To analyze the mechanisms governing the device performance, short circuit current density spectral dependence of the devices fabricated on different types of flexible substrates has been measured. As demonstrated by our analysis, the structures on PEN substrates, besides better substrate transmittance, also show better junction properties.
41
Zhang, Xiaoning, Masudur Rahman, David Neff, and Michael Louis Norton. "DNA origami deposition on native and passivated molybdenum disulfide substrates." Beilstein Journal of Nanotechnology 5 (April 22, 2014): 501–6. http://dx.doi.org/10.3762/bjnano.5.58.
Abstract:
Maintaining the structural fidelity of DNA origami structures on substrates is a prerequisite for the successful fabrication of hybrid DNA origami/semiconductor-based biomedical sensor devices. Molybdenum disulfide (MoS2) is an ideal substrate for such future sensors due to its exceptional electrical, mechanical and structural properties. In this work, we performed the first investigations into the interaction of DNA origami with the MoS2 surface. In contrast to the structure-preserving interaction of DNA origami with mica, another atomically flat surface, it was observed that DNA origami structures rapidly lose their structural integrity upon interaction with MoS2. In a further series of studies, pyrene and 1-pyrenemethylamine, were evaluated as surface modifications which might mitigate this effect. While both species were found to form adsorption layers on MoS2 via physisorption, 1-pyrenemethylamine serves as a better protective agent and preserves the structures for significantly longer times. These findings will be beneficial for the fabrication of future DNA origami/MoS2 hybrid electronic structures.
42
Brown, K. A., E. P. Carpenter, K. A. Watson, J. R. Coggins, A. R. Hawkins, M. H. J. Koch, and D. I. Svergun. "Twists and turns: a tale of two shikimate-pathway enzymes." Biochemical Society Transactions 31, no. 3 (June 1, 2003): 543–47. http://dx.doi.org/10.1042/bst0310543.
Abstract:
We are studying two enzymes from the shikimate pathway, dehydroquinate synthase (DHQS) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Both enzymes have been the subject of numerous studies to elucidate their reaction mechanisms. Crystal structures of DHQS and EPSPS in the presence and absence of substrates, cofactors and/or inhibitors are now available. These structures reveal movements of domains, rearrangements of loops and changes in side-chain positions necessary for the formation of a catalytically competent active site. The potential for using complementary small-angle X-ray scattering (SAXS) studies to confirm the presence of these structural differences in solution has also been explored. Comparative analysis of crystal structures, in the presence and absence of ligands, has revealed structural features critical for substrate-binding and catalysis. We have also analysed these structures by generating GRID energy maps to detect favourable binding sites. The combination of X-ray crystallography, SAXS and computational techniques provides an enhanced analysis of structural features important for the function of these complex enzymes.
43
Chang, Yu-Chung, Bo-Han Huang, and Tsung-Hsien Lin. "Surface-Enhanced Raman Scattering and Fluorescence on Gold Nanogratings." Nanomaterials 10, no. 4 (April 17, 2020): 776. http://dx.doi.org/10.3390/nano10040776.
Abstract:
Surface-enhanced Raman scattering (SERS) spectroscopy is a sensitive sensing technique. It is desirable to have an easy method to produce SERS-active substrate with reproducible and robust signals. We propose a simple method to fabricate SERS-active substrates with high structural homogeneity and signal reproducibility using electron beam (E-beam) lithography without the problematic photoresist (PR) lift-off process. The substrate was fabricated by using E-beam to define nanograting patterns on the photoresist and subsequently coat a layer of gold thin film on top of it. Efficient and stable SERS signals were observed on the substrates. In order to investigate the enhancement mechanism, we compared the signals from this substrate with those with photoresist lifted-off, which are essentially discontinuous gold stripes. While both structures showed significant grating-period-dependent fluorescence enhancement, no SERS signal was observed on the photoresist lifted-off gratings. Only transverse magnetic (TM)-polarized excitation exhibited strong enhancement, which revealed its plasmonic attribution. The fluorescence enhancement showed distinct periodic dependence for the two structures, which is due to the different enhancement mechanism. We demonstrate using this substrate for specific protein binding detection. Similar periodicity dependence was observed. Detailed theoretical and experimental studies were performed to investigate the observed phenomena. We conclude that the excitation of surface plasmon polaritons on the continuous gold thin film is essential for the stable and efficient SERS effects.
44
Terabe, K., A. Gruverman, Y. Matsui, N. Iyi, and K. Kitamura. "Transmission electron microscopy observation and optical property of sol-gel derived LiNbO3 films." Journal of Materials Research 11, no. 12 (December 1996): 3152–57. http://dx.doi.org/10.1557/jmr.1996.0400.
Abstract:
Crystallization behavior, defects, and interface structures of sol-gel derived LiNbO3 films on three kinds of substrates were examined. The nucleation was found to occur epitaxially at the interface between the film and the substrate. The continuous film is formed by coalescence of the island-like crystallites. When sapphire substrate is used, which has large lattice mismatch with the LiNbO3, the resulting film contains a large amount of micropores, twin structures, and misfit dislocations. On the other hand, while LiTaO3 and 5% MgO-doped LiNbO3 substrates with smaller mismatch are used as substrates, the films show no evidence of the formation of dislocations and twins. The film on 5% MgO-doped LiNbO3 substrate shows better optical waveguiding property.
45
Chen, Xiaobo, Jiayue Chen, Bing Yan, Wei Zhang, Luke W. Guddat, Xiang Liu, and Zihe Rao. "Structural basis for the broad substrate specificity of two acyl-CoA dehydrogenases FadE5 from mycobacteria." Proceedings of the National Academy of Sciences 117, no. 28 (June 29, 2020): 16324–32. http://dx.doi.org/10.1073/pnas.2002835117.
Abstract:
FadE, an acyl-CoA dehydrogenase, introduces unsaturation to carbon chains in lipid metabolism pathways. Here, we report that FadE5 fromMycobacterium tuberculosis(MtbFadE5) andMycobacterium smegmatis(MsFadE5) play roles in drug resistance and exhibit broad specificity for linear acyl-CoA substrates but have a preference for those with long carbon chains. Here, the structures ofMsFadE5 andMtbFadE5, in the presence and absence of substrates, have been determined. These reveal the molecular basis for the broad substrate specificity of these enzymes. FadE5 interacts with the CoA region of the substrate through a large number of hydrogen bonds and an unusual π–π stacking interaction, allowing these enzymes to accept both short- and long-chain substrates. Residues in the substrate binding cavity reorient their side chains to accommodate substrates of various lengths. Longer carbon-chain substrates make more numerous hydrophobic interactions with the enzyme compared with the shorter-chain substrates, resulting in a preference for this type of substrate.
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Emelyanov, A. A., M. Yu Plotnikov, N. I. Timoshenko, and I. B. Yudin. "Effective cooling of substrates with low thermal conductivity under conditions of gas-jet MPCVD diamond synthesis." Journal of Physics: Conference Series 2119, no. 1 (December 1, 2021): 012119. http://dx.doi.org/10.1088/1742-6596/2119/1/012119.
Abstract:
Abstract The paper presents the results of an experimental study of heating molybdenum and silicon substrates under the conditions of gas-jet deposition of diamond structures using the precursor gases of a microwave discharge to activate. A cooled substrate holder using a metal melt to improve heat removal by reducing the thermal resistance between the substrate and the substrate holder has been developed. The use of the melt allowed lowering the temperature of the silicon substrate under the conditions of gas-jet deposition to a level that ensures the preservation of its structure. The developed substrate holders were used to carry out gas-jet synthesis of diamond structures on molybdenum and silicon substrates.
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Wang, Xi Shu, Xi Qiao Feng, and Xing Wu Guo. "Failure Behavior of Anodized Coating-Magnesium Alloy Substrate Structures." Key Engineering Materials 261-263 (April 2004): 363–68. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.363.
Abstract:
This work focuses on the damage mechanisms and the resulting failure behavior of structures made of anodized coatings on magnesium alloy substrates. The failure of anodized coatings of about 30µm thickness on AZ91D substrates was investigated under three-points bending loading with online scanning electron microscope (SEM) observations. The obtained SEM images show that void nucleation and crack initiation occurs mainly at sites near the coating-substrate interface, and the evolutionary microcracking damage diffuses from the interface to the coating surface and also to the bulk substrate with the increasing in loading.
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Chaudhary, Santosh Kumar, Jeyaraman Jeyakanthan, and Kanagaraj Sekar. "Structural and functional roles of dynamically correlated residues in thymidylate kinase." Acta Crystallographica Section D Structural Biology 74, no. 4 (April 1, 2018): 341–54. http://dx.doi.org/10.1107/s2059798318002267.
Abstract:
Thymidylate kinase is an important enzyme in DNA synthesis. It catalyzes the conversion of thymidine monophosphate to thymidine diphosphate, with ATP as the preferred phosphoryl donor, in the presence of Mg2+. In this study, the dynamics of the active site and the communication paths between the substrates, ATP and TMP, are reported for thymidylate kinase fromThermus thermophilus. Conformational changes upon ligand binding and the path for communication between the substrates and the protein are important in understanding the catalytic mechanism of the enzyme. High-resolution X-ray crystal structures of thymidylate kinase in apo and ligand-bound states were solved. This is the first report of structures of binary and ternary complexes of thymidylate kinase with its natural substrates ATP and ATP–TMP, respectively. Distinct conformations of the active-site residues, the P-loop and the LID region observed in the apo and ligand-bound structures revealed that their concerted motion is required for the binding and proper positioning of the substrate TMP. Structural analyses provide an insight into the mode of substrate binding at the active site. The residues involved in communication between the substrates were identified through network analysis using molecular-dynamics simulations. The residues identified showed high sequence conservation across species. Biochemical analyses show that mutations of these residues either resulted in a loss of activity or affected the thermal stability of the protein. Further, molecular-dynamics analyses of mutants suggest that the proper positioning of TMP is important for catalysis. These data also provide an insight into the phosphoryl-transfer mechanism.
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Saridakis, Vivian. "Structural-Functional Analysis of USP7." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C309. http://dx.doi.org/10.1107/s2053273314096909.
Abstract:
Ubiquitin Specific Protease 7 (USP7) catalyzes the deubiquitination of several substrate proteins including p53, Mdm2 and UbE2E1. Deubiquitination results in their rescue from 26S proteasome mediated degradation thus USP7 is critical in maintaining the cellular steady state levels of its substrates. USP7 is also known to interact with several viral proteins including herpes simplex virus Infected Cell Protein 0 (ICP0), Epstein Barr Nuclear Antigen 1 (EBNA1) and Kaposi's sarcoma-associated viral interferon regulatory factor 4 (vIRF4). USP7 possesses several domains including an N-terminal TRAF, a catalytic and five ubiquitin-like domains. The crystal structures of several complexes revealed that most substrate proteins interact with the N-terminal domain of USP7 which folds into an eight-stranded antiparallel beta sandwich. EBNA1 and MCM-BP also interact with USP7 through its N-terminal domain in an identical manner to its substrates p53, Mdm2 and UbE2E1 however these proteins are not deubiquitinated by USP7. Substrates that interact with USP7 through its N-terminal domain possess a P/AxxS binding motif. The identification, characterization and structure determination of novel USP7 substrates is ongoing.
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Yamawaki, Yuuki, Tomoki Yufu, and Tamaki Kato. "The Effect of a Peptide Substrate Containing an Unnatural Branched Amino Acid on Chymotrypsin Activity." Processes 9, no. 2 (January 28, 2021): 242. http://dx.doi.org/10.3390/pr9020242.
Abstract:
7-Amino-4-methylcoumarin (AMC) is a low molecular weight fluorescent probe that can be attached to a peptide to enable the detection of specific proteases, such as chymotrypsin, expressed in certain diseases. Because this detection depends on the specificity of the protease toward the peptidyl AMC, the development of specific substrates is required. To investigate the specificity of chymotrypsin, peptidyl AMC compounds incorporating four different amino acid residues were prepared by liquid-phase synthesis. Two unnatural amino acids, 2-amino-4-ethylhexanoic acid (AEH) and cyclohexylalanine (Cha), were used to investigate the substrate specificity as these amino acids have structures different from natural amino acids. AEH was synthesized using diethyl acetamidemalonate as a starting material. The substrate containing Cha had high hydrophobicity and showed a high reaction velocity with chymotrypsin. Although the AEH substrate with a branched side chain had high hydrophobicity, it showed a low reaction velocity. The substrate containing the aromatic amino acid phenylalanine was less hydrophobic than the Cha and AEH substrates, but chymotrypsin showed the highest specificity for this compound. These results demonstrated that the substrate specificity of chymotrypsin is not only affected by the hydrophobicity and aromaticity, but also by the structural expanse of amino acid residues in the substrate.