Zeitschriftenartikel: „Bi-Molecular complexes“

1

Jäger, Martin, Paul Schuler, Hartmut B. Stegmann und Antal Rockenbauer. „Molecular Recognition Analyzed by Observing Intramolecular Interconversion with EPR Spectroscopy“. Zeitschrift für Naturforschung B 53, Nr. 12 (01.12.1998): 1511–19. http://dx.doi.org/10.1515/znb-1998-1215.

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Abstract Molecular recognition between Rebek’s cleft R and 4-(2-benzimidazolyl)-aminomethyl-2,6-di-rm-butyl-phenol (Bi) is investigated by means of EPR spectroscopy. Their specific inter-molecular interactions are distinguished from non-specific interactions represented by mere protonation on addition of benzoic acid. Both interactions are related to intramolecular in terconversions at the C∞-atom of Bi*, where a two-jump mechanism is found for free and protonated Bi* and a two-site exchange for the complexed ligand. While NMR spectroscopy indicates the existence of 1:1 and 1:2 receptor-substrate complexes, the faster time scale of EPR spectroscopy allows to identify one 1 : 2 as well as three 1 : 1 associates and to elucidate their formation conditions. Based upon the corresponding hf parameters, binding modes and sites are proposed for the key-in-the-lock system.

2

Vicente, Ramon, Ànnia Tubau, Saskia Speed, Franz A. Mautner, Florian Bierbaumer, Roland C. Fischer und Salah S. Massoud. „Slow magnetic relaxation and luminescence properties in neodymium(iii)-4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dionato complexes incorporating bipyridyl ligands“. New Journal of Chemistry 45, Nr. 32 (2021): 14713–23. http://dx.doi.org/10.1039/d1nj02583j.

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A new series of eight-coordinated Nd(iii) complexes derived from 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate and bi-pyridyl ligands revealed multifunctional molecular materials as photoluminescent single-molecule magnets (SMMs).

3

Priyadarshini, N., M. Sampath, Shekhar Kumar und U. Kamachi Mudali. „Particle Size Variation and Prediction of Molecular Weight of Bi(III) Hydrolyzed Polymer Using Light Scattering Technique“. ISRN Inorganic Chemistry 2013 (12.02.2013): 1–5. http://dx.doi.org/10.1155/2013/194120.

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The present paper gives an overview of the hydrolysis reactions up to colloid formation of Bi(III) in aqueous nitric acid medium using light-scattering measurements. The hydrolysis products of Bi were polynuclear complexes such as dimers, pentamers, and the most important is the hexameric species. In the present investigation Bi3+ polymers were prepared by diluting different concentrations of Bi(NO3)3·5H2O solutions to pH 1 ± 0.1 by adding 0.1 M NaOH solution as it starts to precipitates at pH 1.4. The degree of polymerization was found to be 5-6 units. Particle size measurements were performed, and it has been found that particle size increases at high concentration of Bi due to aggregation. Refractive index measurements were also performed. The molecular weight of hydrolyzed polymeric species of Bi was determined by using Debye plot, and it was estimated as 1236 Da. The second virial coefficient was found to be 6.24 × 10−3 mLg−1 Da. The present investigation confirms that the predominant complex in the solution has 5-6 Bi atoms.

4

Marfo-owusu, Emmanuel, Keiichi Noguchi und Kenji Okuyama. „The Molecular Complexes of Monoalkylammonium Bromide Salts with (R)-(+)-1,1′-Bi-2-Naphthol and Rac-1,1′-Bi-2-Naphthol“. Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 338, Nr. 1 (01.01.2000): 47–59. http://dx.doi.org/10.1080/10587250008024419.

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5

Younes, Ayman A. O. „Synthesis, biological evaluation and molecular docking studies of novel mixed-ligand Schiff base/8-hydroxyquinoline metal complexes“. Materials Express 13, Nr. 12 (01.12.2023): 2110–27. http://dx.doi.org/10.1166/mex.2023.2564.

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Five manufactured mixed ligands chelate of Schiff base (HL) in the presence of 8-hydroxyquinoline (HQ) with Chromium(III), Cobalt(II), Silver(I) tin(II), and mercury(II) was produced and described. The molecular structure of complexes was examined using physicochemical analysis, thermogravimetric analysis, and spectroscopic methods. Measurements of morphological properties confirm the nano-crystalline particles of the fabricated chelates. FT-IR analysis revealed that HL and HQ chelated with metal ions as NO bi-dentate ligands. The synthesized complexes have distorted octahedral (Cr(III) and Co(II)) and tetrahedral (Ag(I), Sn(II), and Hg(II) forms, according to magnetic and electronic spectrum data. Thermogravimetric (TG) analysis indicates that the formation complexes were stable. The antimicrobial and antiviral effectiveness of ligands and their metal complexes has also been investigated. The results indicated that the newly prepared complexes were greater in activity in contrast to their free ligands, and Studies on molecular docking have been performed out in order to determine the optimal engagement location as well as its inhibitory activity.

6

M. Abd El-Lateef, Hany, Ali M. Ali, Mai M. Khalaf und Aly Abdou. „New iron(III), cobalt(II), nickel(II), copper(II), zinc(II) mixed-ligand complexes: Synthesis, structural, DFT, molecular docking and antimicrobial analysis“. Bulletin of the Chemical Society of Ethiopia 38, Nr. 1 (29.11.2023): 147–66. http://dx.doi.org/10.4314/bcse.v38i1.12.

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The present framework has as its goal the design and synthesis and characterization of new mononuclear 1:1:1 (M:L:Q) mixed-ligand complexes, including FeLQ, CoLQ, NiLQ, CuLQ, and ZnLQ. The "L," is the 4-[(4-oxo-4,5-dihydro-1,3-thiazol-2-yl)hydrazono]methylphenyl 4-methylbenzenesulfonate, while the "Q," is the 8-hydroxy quinoline. According to the findings, L and Q ligands each play the role of a neutral bi-dentate NN and a monobasic bi-dentate ON ligand, respectively. The findings demonstrated an octahedral shape. The density functional theory (DFT) technique was employed, and the quantum chemical descriptors were assessed, to optimize the molecular structure of the compounds. An in vitro investigation was carried out to investigate the antibacterial and antifungal activities of the compounds. According to the findings, the activity of metal complexes as potential candidates for use as antibiotics and antifungals is much greater than that of their free ligands. The in-silico inhibition of the 1fj4 protein was investigated using molecular docking. ZnLQ complex was the one that inhibited the 1fj4 protein with the greatest degree of success. The fact that this is the case lends credence to the notion that these compounds have the potential to function as launchpads for the development of new classes of antibiotics. KEY WORDS: Metal complexes, Schiff-base, Antimicrobial, DFT, Molecular docking Bull. Chem. Soc. Ethiop. 2024, 38(1), 147-166. DOI: https://dx.doi.org/10.4314/bcse.v38i1.12

7

EMANDI, Anca. „Synthesis and Characterization of New Oxovanadium(IV) Coordination Compounds with Pyrazol-5-one Azo Derivatives“. SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 6, Nr. 7 (20.12.1998): 91–99. http://dx.doi.org/10.48141/sbjchem.v6.n7.1998.90_1998_2.pdf.

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A new series of oxovanadium(IV) chelates containing bi-and tridentate pyrazol-5-one azo derivatives ligands of the type (I) [VO(L)2] and (2) [VO(L)(H2O)] have been prepared and characterized by elementary analysis, IR, electronic spectra, conductance measurements, and molecular weights. The ligands coordinate through (O-N) donor system as monobasic and bidentate (HL) for the first type and through (0-N-O) donor system as dibasic and tridentate (H2L) for the second type of complexes. The molecular weights, the presence of the (V=O) stretching band around 950 cm -1, and the visible spectra suggest a monomeric penta-coordinated structure for these complexes.

8

Heshmatpour, Constantin, Jürgen Hauer und František Šanda. „Correlated spectral fluctuations quantified by line shape analysis of fifth-order two-dimensional electronic spectra“. Journal of Chemical Physics 156, Nr. 8 (28.02.2022): 084114. http://dx.doi.org/10.1063/5.0081053.

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Correlated spectral fluctuations were suggested to coordinate excitation transport inside natural light harvesting complexes. We demonstrate the capacities of 2D line shapes from fifth-order coherent electronic signals (R5-2D) to report on such fluctuations in molecular aggregates and present a stochastic approach to fluctuations in correlated site and bi-exciton binding energies in the optical dynamics of Frenkel excitons. The model is applied to R5-2D line shapes of a homodimer, and we show that the peak tilt dynamics are a measure for site energy disorder, inter-site correlation, and the strength of bi-exciton binding energy fluctuations.

9

Lu, Xiao-Qin, Qiang Chen, Xin-Xin Tian, Yue-Wen Mu, Hai-Gang Lu und Si-Dian Li. „Predicting lanthanide boride inverse sandwich tubular molecular rotors with the smallest core–shell structure“. Nanoscale 11, Nr. 44 (2019): 21311–16. http://dx.doi.org/10.1039/c9nr07284e.

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Extensive first-principles theory calculations predict the possibility of bi-decker inverse sandwich complexes La₂[B₁₈], La₂[B₁₈]²⁻, and La₂[B₂@B₁₈], with the B₂-centered La₂[B₂@B₁₈] as a tubular molecular rotor possessing the smallest core–shell structure.

10

Notter, Silke, Carsten Donsbach und Claus Feldmann. „On iodido bismuthates, bismuth complexes and polyiodides with bismuth in the system BiI₃/18-crown-6/I₂“. Zeitschrift für Naturforschung B 76, Nr. 10-12 (18.10.2021): 765–74. http://dx.doi.org/10.1515/znb-2021-0127.

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Abstract The iodido bismuthates [Bi(18-crown-6)I2][BiI4] (1) and [Bi(18-crown-6)I2][Bi3I10] (2), the neutral complex [Bi(C6H14O4)I3](18-crown-6) (3) as well as the polyiodides [Bi(18-crown-6)I2][I5](18-crown-6) (4), [Bi(18-crown-6)I2]2[I14] (5) and [Bi(18-crown-6)I2]2[I19] (6) were prepared by reaction of BiI3, 18-crown-6, and I2 at T = 60–120 °C. The compounds 1–5 were prepared in [n-Bu3MeN][N(Tf)2] as an ionic liquid ([n-Bu3MeN]: tributylmethylammonium, [N(Tf)2]: bis(trifluoromethylsulfonyl)imide), whereas 6 was obtained only by direct reaction of the starting materials. The title compounds exhibit two different constitutions of the [Bi(18-crown-6)I2]+ cation as well as a non-charged, molecular [Bi(C6H14O4)I3] unit with a triethylene glycol ligand generated in situ by cleavage of the crown ether. Infinite chain-like [ BiI 2 / 1 I 4 / 2 ] − ∞ 1 ${}_{\infty }{}^{1}\left[{{\text{BiI}}_{2/1}{\text{I}}_{4/2}\right]}^{-}$ and [ Bi 6 I 18 / 1 I 4 / 2 ∞ 1 ] − ${{}_{\infty }{}^{1}\left[{\text{Bi}}_{6}{\text{I}}_{18/1}{\text{I}}_{4/2}\right]}^{-}$ anions occur in 1 and 2, whereas various polyiodide anions (e.g. [I3]−, [I5]−, [I7]−, [I9]−) with partly complex interaction are observed in 4, 5, and 6. The title compounds were characterized by single-crystal X-ray diffraction analysis and infrared spectroscopy. In the case of 1 and 2, the optical band gap was determined to be E g = 1.91 and 1.62 eV, respectively. Especially, the ionic-liquid-based synthesis affords the different metastable compounds with variable composition and structure in a narrow temperature range.

11

Nasser, Adnan Taleb, und Rafid Al-Asadi. „Schiff Bases Ligands Derived from o-Phthalaldehyde and Their Metal Complexes with Cu2+ and Ni2+: Synthesis, Anti-Breast Cancer and Molecular Docking Study“. Trends in Sciences 20, Nr. 9 (31.03.2023): 5675. http://dx.doi.org/10.48048/tis.2023.5675.

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The Schiff bases and their complexes have an observed biological efficacy, so in the current study it has been prepared, characterized and evaluated the biological activity of some Schiff bases and their metal complexes with copper and nickel and based on ortho-phathaldehyde as a primary compound. A new Schiff bases ligands and metal complexes {[Cu(L)n(H2O)2]Cl2.mH2O and [Ni(L)n].mH2O, where L=N',N'''-((1E,1'E)-1,2-phenylenebis(methanylylidene)) di(benzohydrazide) L1, N',N'''-((1E,1'E)-1,2-phenylenebis (methanylylidene)) di(isonicotinohydrazide) L2, 1,2-bis((E)-(2-(2,4,6-trichlorophenyl)hydrazono)methyl) benzene L3 ; n = 1, 2 ; m = 0, 1, 3/2, 5/2} have been synthesized and elucidated by mass, FT-IR, 13C and 1HNMR, molar conductivity, flame-atomic absorption, magnetic susceptibility, Powder-XRD and TG analysis. The results showed that the L1 and L2 ligands behave as a tetra-dentate donor and were associated with metal ions in a molar ratio of 1:1, while L3 ligand was bi-dentate donor and associated with metal ions in 1:2 molar ratio. In addition, the geometric shapes of the prepared complexes were tetrahedral and square planar for Ni2+ and Zn2+ complexes, and octahedral for Cu2+ complexes. The effect of cellular toxicity in the laboratory has been examined by MTT assay for all compounds against the MCF-7 cancer breast cell line and found to have low efficacy except [Cu(L3)2(H2O)2] Cl2.H2O (5). The copper complex's molecular docking has been performed with breast cancer proteins using the MOE program, and found to target ERα, CDK6 and EGFR proteins by binding to hydrogen bonds and pi-interactions. HIGHLIGHTS Synthesis new chemical compounds, which are some Schiff bases and their metal complexes with copper and nickel ions Characterization of chemical structure of synthesized compounds by mass, FT-IR, 13C and 1HNMR, molar conductivity, flame-atomic absorption, magnetic susceptibility, Powder-XRD and TG analysis Study the biological activity of synthesized compounds as anti-breast cancer Study of molecular docking of compounds that showed biological efficacy with proteins responsible for breast cancer cells GRAPHICAL ABSTRACT

12

Klokishner, Sophia, Serghei Ostrovsky, Andrew Palii und Boris Tsukerblat. „Cooperative Spin Transitions Triggered by Phonons in Metal Complexes Coupled to Molecular Vibrations“. Magnetochemistry 8, Nr. 2 (08.02.2022): 24. http://dx.doi.org/10.3390/magnetochemistry8020024.

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The present article is a short overview of the theoretical modeling of spin transitions in polymetallic compounds. As distinguished from many insightful reviews on this topic, the present work is focused on the nature of cooperative interaction of the metal clusters in molecular crystals with emphasis at the physical role of molecular vibrations and phonons. The underlying model assumes that the cooperativity is triggered by phonons while the metal centers are coupled to molecular vibrations. It is demonstrated that the suggested model gives a satisfactory description of the observed spin transitions in mono-, bi- and tetranuclear compounds. In the framework of the described approach, we discuss the experimental data on spin crossover in the mononuclear [Fe(ptz)6](BF4)2, binuclear [{Fe(bt)(NCS)2}2bpym] and tetranuclear [Fe(tpa){N(CN)2}]4·(BF4)4·(H2O)2 compounds containing iron ions. The approach is also applied to the description of the charge-transfer-induced spin transition in the [{(Tp)Fe(CN)3}{Co-(PY5Me2)}](CF3SO3) complex.

13

Derafa, Wassila, Nadia A.A. Elkanzi, Ali M. Ali und Aly Abdou. „Three Co(II), Ni(II) and Cu(II) Schiff base complexes incorporating 2-[(4-{[(4-methylphenyl)sulfonothioyl]oxy}phenyl)methylene] amino}benzoic acid: Synthesis, structural, dft, biological and molecular docking investigation“. Bulletin of the Chemical Society of Ethiopia 38, Nr. 2 (23.01.2024): 325–46. http://dx.doi.org/10.4314/bcse.v38i2.5.

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New 2-[(4-[(4-methylphenyl)sulfonothioyl)methylene]aminobenzoic acid ligand-Co(II), Ni(II), and Cu(II) complexes are synthesized and characterized in this article. Elemental analysis, mass spectroscopy, conductivity tests, magnetic susceptibility, Fourier transform infrared spectroscopy, thermogravimetric analysis, electronic absorption spectroscopy, and density functional theory calculations were used to determine the coordination mode, and geometry of the synthesized compounds. The Schiff-base ligand was shown to be mono-negatively charged and coordinate to metal ions in a bi-dentate mode through azomethine nitrogen (-CH=N-) and carboxylic Oxygen (-COOH). Density functional theory (DFT) calculations were performed in addition to the experimental data to assess the most probable structures of the complexes. In addition, the biological activities of these compounds were evaluated by in vitro antibacterial and antifungal assays. These novel Co(II), Ni(II), and Cu(II) compounds were shown to be active against a wide variety of microorganisms, including Gram-positive and Gram-negative bacteria, as well as fungi. Following that, molecular docking was used to analyze the complexes' interactions with bacterial proteins, validating the therapeutic potential of the metal-containing compounds. KEY WORDS: Metal complexes, Schiff-base, DFT, Antibacterial, Antifungal, Molecular docking Bull. Chem. Soc. Ethiop. 2024, 38(2), 325-346. DOI: https://dx.doi.org/10.4314/bcse.v38i2.5

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Kalinowski, J., M. Cocchi, L. Murphy, J. A. G. Williams und V. Fattori. „Bi-molecular emissive excited states in platinum (II) complexes for high-performance organic light-emitting diodes“. Chemical Physics 378, Nr. 1-3 (Dezember 2010): 47–57. http://dx.doi.org/10.1016/j.chemphys.2010.09.014.

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15

Boddula, Rajamouli, und Sivakumar Vaidyanathan. „Bi-nuclear luminescent europium(III) molecular complexes for white light emitting diodes: Experimental and theoretical study“. Inorganica Chimica Acta 494 (August 2019): 141–53. http://dx.doi.org/10.1016/j.ica.2019.05.014.

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16

Luo, Yani, Jian Li, Derong Luo, Qingliang You, Zifeng Yang, Tingcheng Li, Xiandan Li und Guangyong Xie. „Methylene-Bridged Tridentate Salicylaldiminato Binuclear Titanium Complexes as Copolymerization Catalysts for the Preparation of LLDPE through [Fe]/[Ti] Tandem Catalysis“. Polymers 11, Nr. 7 (01.07.2019): 1114. http://dx.doi.org/10.3390/polym11071114.

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A novel tandem catalysis system consisted of salicylaldiminato binuclear/mononuclear titanium and 2,6-bis(imino)pyridyl iron complexes was developed to catalyze ethylene in-situ copolymerization. Linear low-density polyethylene (LLDPE) with varying molecular weight and branching degree was successfully prepared with ethylene as the sole monomer feed. The polymerization conditions, including the reaction temperature, the Fi/Ti molar ratio, and the structures of bi- or mononuclear Ti complexes were found to greatly influence the catalytic performances and the properties of obtained polymers. The polymers were characterized by differential scanning calorimetry (DSC), high temperature gel permeation chromatography (GPC) and high temperature 13C NMR spectroscopy, and found to contain ethyl, butyl, as well as some longer branches. The binuclear titanium complexes demonstrated excellent catalytic activity (up to 8.95 × 106 g/molTi·h·atm) and showed a strong positive comonomer effect when combined with the bisiminopyridyl Fe complex. The branching degree can be tuned from 2.53 to 22.89/1000C by changing the reaction conditions or using different copolymerization pre-catalysts. The melting points, crystallinity and molecular weights of the products can also be modified accordingly. The binuclear complex Ti2L1 with methylthio sidearm showed higher capability for comonomer incorporation and produced polymers with higher branching degree and much higher molecular weight compared with the mononuclear analogue.

17

Kovalchukova, Olga V., Al Tahan Rana Abdulilla Abbas, Svetlana B. Strashnova und Pavel V. Strashnov. „Tautomeric transformations and electronic structures of azopyrazolone dyes and their metal complexes“. Reviews in Inorganic Chemistry 38, Nr. 3 (28.08.2018): 87–101. http://dx.doi.org/10.1515/revic-2018-0007.

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AbstractThe features of molecular and electronic structures of complex compounds derived from azopyrazolone derivatives are reviewed. Despite the wide use of metal-containing azopyrazolone dyes for more than 1.5 centuries, little information on their molecular structure is found. Our recent researches allowed the introduction of new coordination modes of azopyrazolone derivatives at complexation with metals. Together with traditional bi- and tridentate coordination, the possibility of an N pyrazolone atom to be involved in coordination was also found. As a result, polymeric or polynuclear complexes were isolated and described by X-ray analysis, NMR, EPR, IR, and UV spectroscopy. The analysis of the interatomic distances in the organic anions indicated that azopyrazolone derivatives do not undergo significant azo-hydrazo tautomeric transformations at ionization and complexation despite strong shifts of the absorption bands in their IR and UV-VIS spectra.

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Braunschweig, Holger, Peter B. Brenner, Rian D. Dewhurst und Krzysztof Radacki. „A Base-stabilized Iodoborylene Complex of Platinum(II)“. Zeitschrift für Naturforschung B 68, Nr. 5-6 (01.06.2013): 747–49. http://dx.doi.org/10.5560/znb.2013-3079.

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The first base-stabilized iodoborylene platinum complex was prepared through the addition of 4-picoline (4-Pic) to a suspension of an iodo-bridged binuclear iodoboryl complex. An X-ray structure determination of the title compound has characterized the molecular structure as cis-[Pt{BI(4- Pic)}I2(PCy3)]. The bond lengths lie in the expected range for neutral, base-stabilized borylene complexes. The strong trans influence of the borylene moiety is reflected in the longer Pt-1 distance for the iodo ligand opposite the borylene, compared to that opposite the phosphine ligand

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Lukov, V. V., I. N. Shcherbakov, S. I. Levchenkov, Yu P. Tupolova, L. D. Popov, I. V. Pankov und S. V. Posokhova. „Controlled Molecular Magnetism of Bi- and Polynuclear Transition Metal Complexes Based on Hydrazones, Azomethines, and Their Analogs“. Russian Journal of Coordination Chemistry 45, Nr. 3 (März 2019): 163–87. http://dx.doi.org/10.1134/s1070328419030060.

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20

Marfo-Owusu, Emmanuel, Kenji Okuyama und Keiichi Noguchi. „THE CRYSTAL STRUCTURES OF 1:1 MOLECULAR COMPLEXES OF MONOALKYLAMMONIUM HALIDES WITH RAC-1,1′-BI-2-NAPHTHOL“. Molecular Crystals and Liquid Crystals 399, Nr. 1 (01.01.2003): 29–42. http://dx.doi.org/10.1080/15421400390223167.

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21

Diemer, Rolf, Uwe Dittes, Bernhard Nuber, Volker Seifried, Wolfgang Opferkuch und Bernhard K. Keppler. „Synthesis, Characterization and Molecular Structures of some Bismuth(III) Complexes with Thiosemicarbazones and Dithiocarbazonic Acid Methylester Derivatives with Activity against Helicobacter Pylori“. Metal-Based Drugs 2, Nr. 5 (01.01.1995): 271–92. http://dx.doi.org/10.1155/mbd.1995.271.

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The reactions of bismuth(III) nitrate pentahydrate and bismuth(III) chloride with heterocyclic thiosemicarbazones and derivatives of dithiocarbazonic acid methylester were used to synthesize the respective bismuth(III) complexes, which could be divided into five groups D-H because of their stoichiometrical properties and their molecular structures. The molecular structure and the near coordination sphere of the bismuth(III) central atom of four representative compounds were determined by single-crystal X-ray studies. Bis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N3,S]bismuth(III) nitrate (5) belongs to group D. The two tridentate ligands and the nitrate ion surround the bismuth atom. The best description of the coordination sphere appears to be that of a distorted trigonal dodecahedron with one position occupied by the lone pair of the bismuth atom. Bis[1-azepanyl-4-(2-thienyl)-2,3-diazapenta-1,3-diene-1-thiolato-N3,S]bismuth(III) nitrate (9) is assigned to complex type E. Here, two deprotonated ligand molecules are coordinated to the bismuth(III) central atom as bidentate ligands. The structure of this complex can best be described as a distorted trigonal antiprism with a five-coordinated central atom. The two triangular faces are formed by the atoms S(4), N(6), O(11) and S(3), N(4) and the lone pair of the central atom. The two chelate rings are almost perpendicular to each other. Complex molecules of group F form dimeric units with bichloro-bridged bismuth atoms. The structure of di-μ-chlorobis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N3,S-chloro]dibismuth(III) (15) can be described as two six-coordinated bismuth atoms, which are bound together via two bridging chlorine atoms. The two bismuth atoms Bi(1) and Bi(1a) and the two bridging chlorine atoms Cl(2) and Cl(2a) form the Bi2Cl2 plane. The two tridentate ligand molecules coordinate via the same atoms as shown in complex 5. In addition, they form two parallel planes, which are perpendicular to the Bi2Cl2 plane. With regard to the center of the Bi(1)-Bi(2) axis they are central point symmetrical, i.e. one pyridine ring lies above and the other beneath the Bi2Cl2 plane. Bismuth(III) chloride and pyridine-2-carboxaldehydethiosemicarbazone 1 b or 2-acetylpyridine-thiosemicarbazone 1 c form complexes of group G. Three chlorine atoms and a bidentate ligand are coordinated to the bismuth(III) central atom. The bidentate ligand bound to the central atom through the N(3) atom and the sulfur atom of the thioketo group. The structure of 18 is completely different from the structures of the bismuth(III) complexes discussed so far and was therefore assigned to group H. The bismuth central atom is coordinated with two ligands, which are bound in different ways. One of them is deprotonated. This ligand is bound to the central atom via the sulfur atom S(3) of the thiolate group and the N(5) atom. An interaction between the sulfur atom of the thiophene ring and the bismuth atom is not possible.The other ligand molecule is not deprotonated. This ligand is bound to the bismuth(III) cation merely via the sulfur atom S(1) of the thioketo group. The best description of the coordination sphere of the bismuth atom is that of a distorted square bipyramidal polyhedron. The square face is formed by the atoms S(3), N(5), Cl(1), the lone pair and the bismuth atom within. The axial positions are occupied by the atoms S(1) and Cl(2). The bond angle between S(1), Bi(1) and Cl(2) differs by about eight degrees from the value determined for a regular square bipyramidal polyhedron of 180 degrees.Some of the newly synthesized bismuth complexes and three ligands have been tested against several strains of Helicobacter pylori bacteria in an agar dilution test. Almost all of the listed bismuth complexes show excellent inhibitory properties with regard to growth of H. pylori already at low concentrations.

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Katkova, Marina A., Grigory Y. Zhigulin, Roman V. Rumyantcev, Galina S. Zabrodina, Vladimir R. Shayapov, Maxim N. Sokolov und Sergey Y. Ketkov. „Water-Soluble Bismuth(III) Polynuclear Tyrosinehydroximate Metallamacrocyclic Complex: Structural Parallels to Lanthanide Metallacrowns“. Molecules 25, Nr. 19 (23.09.2020): 4379. http://dx.doi.org/10.3390/molecules25194379.

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Recently there has been a great deal of interest and associated research into aspects of the coordination chemistry of lanthanides and bismuth—elements that show intriguing common features. This work focuses on the synthesis and characterization of a novel bismuth(III) polynuclear metallamacrocyclic complex derived from aminohydroxamic acid, in order to compare the coordination ability of Bi3+ with the similarly sized La3+ ions. A polynuclear tyrosinehydroximate Bi(OH)[15-MCCu(II)Tyrha-5](NO3)2 (1) was obtained according to the synthetic routes previously described for water-soluble Ln(III)-Cu(II) 15-MC-5 metallacrowns. Correlations between structural parameters of Bi(III) and Ln(III) complexes were analyzed. DFT calculations confirmed the similarity between molecular structures of the model bismuth(III) and lanthanum(III) tyrosinehydroximate 15-metallacrowns-5. Analysis of the electronic structures revealed, however, stronger donor-acceptor interactions between the central ion and the metallamacrocycle in the case of the lanthanum analogue. Thermochromic properties of 1 were studied.

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Gong, Jingyi, Thomas N. Gaitanos, Olivia Luu, Yunyun Huang, Louise Gaitanos, Jana Lindner, Rudolf Winklbauer und Rüdiger Klein. „Gulp1 controls Eph/ephrin trogocytosis and is important for cell rearrangements during development“. Journal of Cell Biology 218, Nr. 10 (13.08.2019): 3455–71. http://dx.doi.org/10.1083/jcb.201901032.

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Trogocytosis, in which cells nibble away parts of neighboring cells, is an intercellular cannibalism process conserved from protozoa to mammals. Its underlying molecular mechanisms are not well understood and are likely distinct from phagocytosis, a process that clears entire cells. Bi-directional contact repulsion induced by Eph/ephrin signaling involves transfer of membrane patches and full-length Eph/ephrin protein complexes between opposing cells, resembling trogocytosis. Here, we show that the phagocytic adaptor protein Gulp1 regulates EphB/ephrinB trogocytosis to achieve efficient cell rearrangements of cultured cells and during embryonic development. Gulp1 mediates trogocytosis bi-directionally by dynamic engagement with EphB/ephrinB protein clusters in cooperation with the Rac-specific guanine nucleotide exchange factor Tiam2. Ultimately, Gulp1’s presence at the Eph/ephrin cluster is a prerequisite for recruiting the endocytic GTPase dynamin. These results suggest that EphB/ephrinB trogocytosis, unlike other trogocytosis events, uses a phagocytosis-like mechanism to achieve efficient membrane scission and engulfment.

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Mengele, Alexander K., Carolin Müller, Djawed Nauroozi, Stephan Kupfer, Benjamin Dietzek und Sven Rau. „Molecular Scylla and Charybdis: Maneuvering between pH Sensitivity and Excited-State Localization in Ruthenium Bi(benz)imidazole Complexes“. Inorganic Chemistry 59, Nr. 17 (26.08.2020): 12097–110. http://dx.doi.org/10.1021/acs.inorgchem.0c01022.

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Martins, Evandro Paulo Soares, und Gerd B. Rocha. „Performance assessment of semiempirical molecular orbital methods in the structural prediction of Sb(III) and Bi(III) complexes“. Journal of Molecular Modeling 19, Nr. 10 (20.08.2013): 4575–84. http://dx.doi.org/10.1007/s00894-013-1974-x.

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Mehmood, Mehwish, Imtiaz-ud-Din., Anham Zafar, Azhar Iqbal, Maria Mukhtar und Muhammad Nawaz Tahir. „Molecular architecture, characterization, and applications of homoleptic heteronuclear 3d/4f metals’ complexes derived from bi-compartmental Schiff-base“. Journal of Molecular Structure 1274 (Februar 2023): 134547. http://dx.doi.org/10.1016/j.molstruc.2022.134547.

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Qian, Zhe, Ying Zhang, Ai-Quan Jia, Hua-Tian Shi und Qian-Feng Zhang. „Syntheses, molecular structures, and spectroscopic properties of manganese(II)/(III) complexes with tetraphenylimidodiphosphinato and bi-pyridine or salicylaldehyde ligands“. Inorganica Chimica Acta 502 (März 2020): 119298. http://dx.doi.org/10.1016/j.ica.2019.119298.

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Biertümpel, Ingo, und Hans-Herbert Schmidtke. „Evaluation of Luminescence Decay Measurements Probed on Pure and Doped Pt(IV) Hexahalogeno Complexes. II. Molecular Properties Obtained from Temperature Dependent Lifetime Curves“. Zeitschrift für Naturforschung A 52, Nr. 5 (01.05.1997): 447–56. http://dx.doi.org/10.1515/zna-1997-0513.

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Abstract Lifetime measurements down to nearly liquid helium temperatures are used for determining energy levels and transition rates between excited levels and relaxations into the ground state. Energies are obtained from temperature dependent lifetimes by fitting experimental curves to model functions pertinent for thermally activated processes. Rates are calculated from solutions of rate equations. Similar parameters for pure and doped Pt(IV) hexahalogeno complexes indicate that excited levels largely belong to molecular units. Some of the rates between excited states are only somewhat larger than decay rates into the ground state, which is a consequence of the polyexponential decay measured also at low temperature (2 K). In the series of halogen complexes, the rates between spinorbit levels resulting from 3T1g increase from fluorine to bromine, although energy splittings become larger. Due to the decreasing population of higher excited states in this series, K^PtFö shows a tri-exponential, K2PtCl6 a bi-exponential and FoPtBr6 a mono-exponential decay. In the latter case the population density of higher excited states relaxes so fast that emission occurs primarily from the lowest excited Γ3(3T1g) level. Phase transitions and emission from chromophores on different sites can also be observed.

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RICHANI, Dulama, Yiqing ZHAO, Xiuhua LIAO, Jared M. CAMPBELL, Abbas HABIBALAHI, William A. STOCKER, Ewa M. GOLDYS, Craig A. HARRISON und Robert B. GILCHRIST. „Novel Oocyte-Secreted Factors Improve Mouse IVM Outcomes“. Fertility & Reproduction 04, Nr. 03n04 (September 2022): 132. http://dx.doi.org/10.1142/s2661318222740449.

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Background: In vitro maturation (IVM) is a technology designed to obtain mature oocytes following culture of immature cumulus–oocyte complexes (COC) in vitro. IVM is characterized by minimal patient stimulation, making it attractive for patients with excessive AFC or those requiring immediate fertility preservation. However, the clinical uptake of IVM has been slow, primarily due to lower embryo yield and live birth rate relative to IVF, therefore improving IVM culture is required. Aim: To assess whether supplementation of IVM culture medium with the novel in-house engineered TGFβ proteins cumulin and super-GDF9 improves subsequent embryo development. Method: Immature mouse COCs were cultured by standard IVM or bi-phasic IVM ± cumulin or super-GDF9. Following IVM, cumulus expansion was scored and COCs were fertilized, and cultured to assess embryo development. Differential staining was performed on day 6 blastocysts following bi-phasic IVM to assess cell allocation. In a separate experiment, hyperspectral imaging of autofluorescence was carried out on oocytes and cumulus cells following standard IVM ± cumulin to assess the molecular composition of these cells. Results: Both cumulin and super-GDF9 in standard IVM significantly increased cumulus expansion (P<0001; n=104-115 COCs) and blastocyst rate (53.9% control, 73.6% cumulin, 70.4% super-GDF9; P=0.006; n=382-406 oocytes). Hyperspectral imaging showed that oocytes (n=115-158) and cumulus cells (n=532-600) exposed to cumulin during IVM had a distinct spectral profile that varied dramatically (P<0.005) from untreated cells, demonstrating that cumulin has a major impact on the molecular composition of these cells, likely contributing to the improved oocyte quality. In bi-phasic IVM, cumulin did not significantly alter embryo yield (n=387-424 oocytes) or blastocyst cell number or allocation (n=84-112 blastocysts). Conclusion: Cumulin did not provide an additional beneficial effect in bi-phasic IVM, however in standard IVM, cumulin and super-GDF9 significantly improve oocyte developmental competence suggesting that their effects in human IVM should be investigated.

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Schedler, Benno, Olessya Yukhnovets, Lennart Lindner, Alida Meyer und Jörg Fitter. „The Thermodynamic Fingerprints of Ultra-Tight Nanobody–Antigen Binding Probed via Two-Color Single-Molecule Coincidence Detection“. International Journal of Molecular Sciences 24, Nr. 22 (15.11.2023): 16379. http://dx.doi.org/10.3390/ijms242216379.

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Life on the molecular scale is based on a versatile interplay of biomolecules, a feature that is relevant for the formation of macromolecular complexes. Fluorescence-based two-color coincidence detection is widely used to characterize molecular binding and was recently improved by a brightness-gated version which gives more accurate results. We developed and established protocols which make use of coincidence detection to quantify binding fractions between interaction partners labeled with fluorescence dyes of different colors. Since the applied technique is intrinsically related to single-molecule detection, the concentration of diffusing molecules for confocal detection is typically in the low picomolar regime. This makes the approach a powerful tool for determining bi-molecular binding affinities, in terms of KD values, in this regime. We demonstrated the reliability of our approach by analyzing very strong nanobody-EGFP binding. By measuring the affinity at different temperatures, we were able to determine the thermodynamic parameters of the binding interaction. The results show that the ultra-tight binding is dominated by entropic contributions.

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Uson, Rafael, Juan Fornies, Milagros Tomas, Irene Ara und Jose M. Casas. „Bi- and trinuclear platinum-silver complexes with or without platinum-silver bonds. Molecular structure of [PPh3(C6Cl5)ClPt(.mu.-Cl)AgPPh3]“. Inorganic Chemistry 28, Nr. 12 (Juni 1989): 2388–92. http://dx.doi.org/10.1021/ic00311a027.

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Imai, Yoshitane, Nobuo Tajima, Tomohiro Sato und Reiko Kuroda. „Visualization of Molecular Recognition: A Novel System Based on Charge-Transfer Complexes Composed of 1,1‘-Bi-2-naphthol Derivatives andp-Benzoquinone“. Organic Letters 8, Nr. 14 (Juli 2006): 2941–44. http://dx.doi.org/10.1021/ol060862q.

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ALBEDAIR, Lamia A. „Iron(III), gold(III), platinum(IV) and palladium(II) trimethoprim drug complexes: synthesis, spectroscopic, morphological and anticancer assessments“. Revue Roumaine de Chimie 65, Nr. 12 (2021): 1145–52. http://dx.doi.org/10.33224/rrch.2020.65.12.09.

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Iron(III), gold(III), platinum(IV) and palladium(II) complexes of trimethoprim (TMP) drug were synthesized and well characterized using elemental analysis, conductance measurements, (UV-Vis, FTIR, 1HNMR and X-ray powder diffraction) spectroscopy. The Au(III), Pt(IV) and Pd(II) complexes have a four coordinate geometry comprising one molecules of the TMP drug and two coordinated chloride ions, while, iron(III) complex has an octahedral geometry containing one TMP, three chloride and one coordinated water molecules. The TMP drug acts as a bi-dentate chelate towards the metal ions through the nitrogen atoms of the two amino groups attached with pyrimidine ring, this was confirmed by spectroscopic analyses with the molecular formulas [Fe(TMP)Cl3(H2O)].4H2O, [Au(TMP)Cl2]Cl2H2O, [Pt(TMP)Cl2]Cl22H2O and [Pd(TMP)Cl2]. The transmission electron microscopy (TEM) and XRD analyses deduced that the gold(III) complex has a nano-scale range at ~ 10 nm. The [Au(TMP)Cl2]Cl2H2O complex was screened for its cytotoxicity evaluation against hepatocellular carcinoma (HepG2) and colon carcinoma (HCT-116) cell lines. It is showed that the IC50 of gold(III) complex are 7.46 µg/mL and 9.30 µg/mL against HepG2 and HCT-116 cancer cell lines, respectively.

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Du, Pingwu, Jacob Schneider, Fan Li, Wei Zhao, Upali Patel, Felix N. Castellano und Richard Eisenberg. „Bi- and Terpyridyl Platinum(II) Chloro Complexes: Molecular Catalysts for the Photogeneration of Hydrogen from Water or Simply Precursors for Colloidal Platinum?“ Journal of the American Chemical Society 130, Nr. 15 (April 2008): 5056–58. http://dx.doi.org/10.1021/ja711090w.

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Silveira, Célia M., Lidia Zuccarello, Catarina Barbosa, Giorgio Caserta, Ingo Zebger, Peter Hildebrandt und Smilja Todorovic. „Molecular Details on Multiple Cofactor Containing Redox Metalloproteins Revealed by Infrared and Resonance Raman Spectroscopies“. Molecules 26, Nr. 16 (11.08.2021): 4852. http://dx.doi.org/10.3390/molecules26164852.

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Vibrational spectroscopy and in particular, resonance Raman (RR) spectroscopy, can provide molecular details on metalloproteins containing multiple cofactors, which are often challenging for other spectroscopies. Due to distinct spectroscopic fingerprints, RR spectroscopy has a unique capacity to monitor simultaneously and independently different metal cofactors that can have particular roles in metalloproteins. These include e.g., (i) different types of hemes, for instance hemes c, a and a3 in caa3-type oxygen reductases, (ii) distinct spin populations, such as electron transfer (ET) low-spin (LS) and catalytic high-spin (HS) hemes in nitrite reductases, (iii) different types of Fe-S clusters, such as 3Fe-4S and 4Fe-4S centers in di-cluster ferredoxins, and (iv) bi-metallic center and ET Fe-S clusters in hydrogenases. IR spectroscopy can provide unmatched molecular details on specific enzymes like hydrogenases that possess catalytic centers coordinated by CO and CN− ligands, which exhibit spectrally well separated IR bands. This article reviews the work on metalloproteins for which vibrational spectroscopy has ensured advances in understanding structural and mechanistic properties, including multiple heme-containing proteins, such as nitrite reductases that house a notable total of 28 hemes in a functional unit, respiratory chain complexes, and hydrogenases that carry out the most fundamental functions in cells.

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Deng, Rui, Ke Wu, Jiawei Lin, Dehang Wang, Yuanyuan Huang, Yang Li, Zhenkun Shi et al. „DeepSub: Utilizing Deep Learning for Predicting the Number of Subunits in Homo-Oligomeric Protein Complexes“. International Journal of Molecular Sciences 25, Nr. 9 (28.04.2024): 4803. http://dx.doi.org/10.3390/ijms25094803.

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The molecular weight (MW) of an enzyme is a critical parameter in enzyme-constrained models (ecModels). It is determined by two factors: the presence of subunits and the abundance of each subunit. Although the number of subunits (NS) can potentially be obtained from UniProt, this information is not readily available for most proteins. In this study, we addressed this gap by extracting and curating subunit information from the UniProt database to establish a robust benchmark dataset. Subsequently, we propose a novel model named DeepSub, which leverages the protein language model and Bi-directional Gated Recurrent Unit (GRU), to predict NS in homo-oligomers solely based on protein sequences. DeepSub demonstrates remarkable accuracy, achieving an accuracy rate as high as 0.967, surpassing the performance of QUEEN. To validate the effectiveness of DeepSub, we performed predictions for protein homo-oligomers that have been reported in the literature but are not documented in the UniProt database. Examples include homoserine dehydrogenase from Corynebacterium glutamicum, Matrilin-4 from Mus musculus and Homo sapiens, and the Multimerins protein family from M. musculus and H. sapiens. The predicted results align closely with the reported findings in the literature, underscoring the reliability and utility of DeepSub.

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Borovyk, Polina, Mariia Litvinchuk, Anton Bentya, Svitlana Orysyk, Yurii Zborovskiy und Nataliia Slyvka. „Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization“. Ukrainian Chemistry Journal 85, Nr. 3 (07.06.2019): 3–19. http://dx.doi.org/10.33609/0041-6045.85.3.2019.3-19.

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The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

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Borovyk, Polina, Mariia Litvinchuk, Anton Bentya, Svitlana Orysyk, Yurii Zborovskiy und Nataliia Slyvka. „Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization“. Ukrainian Chemistry Journal 85, Nr. 3 (07.06.2019): 3–19. http://dx.doi.org/10.33609/6045.85.3.2019.3-19.

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The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

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Peeters, Bas W. A., Alexandra C. A. Piët und Maarten Fornerod. „Generating Membrane Curvature at the Nuclear Pore: A Lipid Point of View“. Cells 11, Nr. 3 (29.01.2022): 469. http://dx.doi.org/10.3390/cells11030469.

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In addition to its structural role in enclosing and protecting the genome, the nuclear envelope (NE) forms a highly adaptive communication interface between the cytoplasm and the nuclear interior in eukaryotic cells. The double membrane of the NE is perforated by nuclear pores lined with large multi-protein structures, called nuclear-pore complexes (NPCs), which selectively allow the bi-directional transport of ions and macromolecular cargo. In order to nucleate a pore, the inner and outer nuclear membrane have to fuse at the site of NPC insertion, a process requiring both lipid bilayers to be deformed into highly curved structures. How this curvature is achieved and which factors are involved in inducing and stabilizing membrane curvature at the nuclear pore remain largely unclear. In this review, we will summarize the molecular mechanisms thought to be involved in membrane curvature generation, with a particular emphasis on the role of lipids and lipid metabolism in shaping the nuclear pore membrane.

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Hagan, Iain M., und Agnes Grallert. „Spatial control of mitotic commitment in fission yeast“. Biochemical Society Transactions 41, Nr. 6 (20.11.2013): 1766–71. http://dx.doi.org/10.1042/bst20130190.

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The activation of the Cdk1 (cyclin-dependent kinase 1)–cyclin B complex to promote commitment to mitosis is controlled by the phosphorylation status of the Cdk1 catalytic subunit. Cdk1 phosphorylation by Wee1 kinases blocks activation until Cdc25 (cell division cycle 25) phosphatases remove this phosphate to drive division. Feedback inhibition of Wee1 and promotion of Cdc25 activities by the newly activated Cdk1–cyclin B complexes ensure that the transition from interphase to mitosis is a rapid and complete bi-stable switch. Although this level of molecular understanding of the mitotic commitment switch has been clear for over two decades, it is still unclear how the switch is engaged to promote division at the right time for a particular context. We discuss recent work in fission yeast that shows how the spatial organization of signalling networks, in particular events on the centrosome equivalent, the spindle pole body, plays a key role in ensuring that the timing of cell division is coupled to environmental cues.

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Danilkovich, A. V., D. A. Tikhonov und V. M. Lipkin. „Dynamics of 24 Self-Assembling H-(RADA)4-OH Peptides Complexed in Bi-Layered Structure with Layers in syn and anti Orientation“. Биоорганическая химия 49, Nr. 3 (01.05.2023): 306–18. http://dx.doi.org/10.31857/s0132342323030107.

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H-(RADA)4-OH peptide in water tends to form biolgels at physiological conditions. Thusly made scaffold is formed of fibrils resulted from peptides self-assembling. Fibrils have two external hydrophilic layers, while hydrophobic one is situated between of them. Bio gels by the H-(RADA)4-OH peptides are considered to be a prominent source for designed extra cellular matrix aimed to cell cultures of different types. Little is known about detailed structure the filament structure and β-sheets peptide composition. We have designed and studied molecular dynamics of bi-layered protofilament structures with β-sheets formed of parallel or anti-parallel peptide chains. Method of molecular dynamics was used to study H-(RADA)4-OH peptide complexes at 80 and 300 K. While the most stable peptide complex was found to consist of anti-parallel peptides, had the lowest free energy and the least deviation of atom coordinates, yet another stable structure of the peptide complex was identified as 24-mer of parallel peptides with two β-sheets placed in syn orientation. These results underlined the importance of factors, directing the initial stages of the H-(RADA)4-OH peptide self-assembling in solution.

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Pangburn, M. K., und N. Rawal. „Structure and function of complement C5 convertase enzymes“. Biochemical Society Transactions 30, Nr. 6 (01.11.2002): 1006–10. http://dx.doi.org/10.1042/bst0301006.

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The multisubunit enzymes of the complement system that cleave C5 have many unusual properties, the most striking of which is that they acquire their specificity for C5 following cleavage of another substrate C3. C5 convertases are assemblies of two proteins C4b and C2a (classical or lectin pathways) or C3b and Bb (alternative pathway) and additional C3b molecules. The catalytic complexes (C4b, C2a or C3b, Bb) are intrinsically unstable (t1,2 = 1–3 min) and the enzymes are controlled by numerous regulatory proteins that accelerate this natural decay rate. Immediately after assembly, the bi-molecular enzymes preferentially cleave the protein C3 and exhibit poor activity toward C5 (a Km of approx. 25 μM and a C5 cleavage rate of 0.3-1 C5/min at Vmax). Efficient C3 activation results in the covalent attachment of C3b to the cell surface and to the enzyme itself, resulting in formation of C3b-C3b and C4b-C3b complexes. Our studies have shown that deposition of C3b alters the specificity of the enzymes of both pathways by changing the Km for C5 more than 1000-fold from far above the physiological C5 concentration to far below it. Thus, after processing sufficient C3 at the surface of a microorganism, the enzymes switch to processing C5, which initiates the formation of the cytolytic membrane attack complex of complement.

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He, Yonghui, Yannan Bin, Yizeng Liang und Juan Xiang. „Density functional investigation of the molecular structures, vibrational and absorption spectra of metal thiolate complexes, M(SC6H5)3 (M=As, Sb or Bi)“. Computational and Theoretical Chemistry 994 (August 2012): 91–96. http://dx.doi.org/10.1016/j.comptc.2012.06.023.

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Zhang, Xin, Timothy J. Prior, Kai Chen, Orlando Santoro und Carl Redshaw. „Ring Opening Polymerization of Lactides and Lactones by Multimetallic Titanium Complexes Derived from the Acids Ph2C(X)CO2H (X = OH, NH2)“. Catalysts 12, Nr. 9 (24.08.2022): 935. http://dx.doi.org/10.3390/catal12090935.

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The reactions of the titanium alkoxide [Ti(OR)4] (R = Me, nPr, iPr, tBu) with the acids 2,2’-Ph2C(X)(CO2H), where X = OH and NH2, i.e., benzilic acid (2,2’-diphenylglycolic acid, L1H2), and 2,2’-diphenylglycine (L2H3), have been investigated. The variation of the reaction stoichiometry allows for the isolation of mono-, bi-, tri or tetra-metallic products, the structures of which have been determined by X-ray crystallography. The ability of the resulting complexes to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and r-lactide (r-LA) has been investigated. In the case of ε-CL, all catalysts except that derived from [Ti(OnPr)4] and L2H3, i.e., 7, exhibited an induction period of between 60 and 285 min, with 7 exhibiting the best performance (>99% conversion within 6 min). The PCL products are moderate- to high-molecular weight polymers. For r-LA, systems 1, 3, 4 and 7 afforded conversions of ca. 90% or more, with 4 exhibiting the fastest kinetics. The molecular weights for the PLA are somewhat higher than those of the PCL, with both cyclic and linear PLA products (end groups of OR/OH) identified. Comparative studies versus the [Ti(OR)4] starting materials were conducted, and although high conversions were achieved, the control was poor.

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Ma, Xiuyan, Yunfei Hu, Hossein Batebi, Jie Heng, Jun Xu, Xiangyu Liu, Xiaogang Niu et al. „Analysis of β2AR-Gs and β2AR-Gi complex formation by NMR spectroscopy“. Proceedings of the National Academy of Sciences 117, Nr. 37 (31.08.2020): 23096–105. http://dx.doi.org/10.1073/pnas.2009786117.

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The β2-adrenergic receptor (β2AR) is a prototypical G protein-coupled receptor (GPCR) that preferentially couples to the stimulatory G protein Gs and stimulates cAMP formation. Functional studies have shown that the β2AR also couples to inhibitory G protein Gi, activation of which inhibits cAMP formation [R. P. Xiao, Sci. STKE 2001, re15 (2001)]. A crystal structure of the β2AR-Gs complex revealed the interaction interface of β2AR-Gs and structural changes upon complex formation [S. G. Rasmussen et al., Nature 477, 549–555 (2011)], yet, the dynamic process of the β2AR signaling through Gs and its preferential coupling to Gs over Gi is still not fully understood. Here, we utilize solution nuclear magnetic resonance (NMR) spectroscopy and supporting molecular dynamics (MD) simulations to monitor the conformational changes in the G protein coupling interface of the β2AR in response to the full agonist BI-167107 and Gs and Gi1. These results show that BI-167107 stabilizes conformational changes in four transmembrane segments (TM4, TM5, TM6, and TM7) prior to coupling to a G protein, and that the agonist-bound receptor conformation is different from the G protein coupled state. While most of the conformational changes observed in the β2AR are qualitatively the same for Gs and Gi1, we detected distinct differences between the β2AR-Gs and the β2AR-Gi1 complex in intracellular loop 2 (ICL2). Interactions with ICL2 are essential for activation of Gs. These differences between the β2AR-Gs and β2AR-Gi1 complexes in ICL2 may be key determinants for G protein coupling selectivity.

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Wu, Jianfang, Carmen Sousa und Coen de Graaf. „The Role of Vibrational Anharmonicity in the Computational Study of Thermal Spin Crossover“. Magnetochemistry 5, Nr. 3 (02.09.2019): 49. http://dx.doi.org/10.3390/magnetochemistry5030049.

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Spin crossover in transition metal complexes can be studied in great detail with computational chemistry. Over the years, the understanding has grown that the relative stability of high-spin (HS) versus low-spin (LS) states is a subtle balance of many factors that all need to be taken into account for a reliable description. Among the different contributions, the zero-point energy (ZPE) and the entropy play key roles. These quantities are usually calculated assuming a harmonic oscillator model for the molecular vibrations. We investigated the impact of including anharmonic corrections on the ZPE and the entropy and indirectly on the critical temperature of spin crossover. As test systems, we used a set of ten Fe(II) complexes and one Fe(III) complex, covering different coordination modes (mono-, bi-, and tri-dentate ligands), decreasing coordination number upon spin crossover, coordination by second- and third-row atoms, and changes in the oxidation state. The results show that the anharmonicity has a measurable effect, but it is in general rather small, and tendencies are not easily recognized. As a conclusion, we put forward that for high precision results, one should be aware of the anharmonic effects, but as long as computational chemistry is still struggling with other larger factors like the influence of the environment and the accurate determination of the electronic energy difference between HS and LS, the anharmonicity of the vibrational modes is a minor concern.

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Krenács, T., H. Uda und S. Tanaka. „One-step double immunolabeling of mouse interdigitating reticular cells: simultaneous application of pre-formed complexes of monoclonal rat antibody M1-8 with horseradish peroxidase-linked anti-rat immunoglobulins and of monoclonal mouse anti-Ia antibody with alkaline phosphatase-coupled anti-mouse immunoglobulins.“ Journal of Histochemistry & Cytochemistry 39, Nr. 12 (Dezember 1991): 1719–23. http://dx.doi.org/10.1177/39.12.1940324.

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A novel one-step double immunolabeling method was elaborated on the basis of the simultaneous application of preformed molecular complexes of two primary antibodies with their specific secondary antibodies labeled with different enzymes. Treatment with a rat monoclonal antibody (MAb), M1-8, pre-coupled with horseradish peroxidase-linked sheep anti-rat immunoglobulins, and enzyme reaction revealed by the 3-amino-9-ethylcarbazole/hydrogen peroxide reaction, resulted in red-brown intracytoplasmic staining of interdigitating reticular cells in the lymph nodes of Balb/c mice. Another molecular complex, made of mouse anti-Ia MAb with alkaline phosphatase-linked rabbit anti-mouse immunoglobulins, applied at the same time and then developed with naphthol AS-BI-phosphate/fast blue BB as substrate, yielded blue surface staining of this cell type in addition to labeling of B-lymphocytes. The method described provides the possibility of relatively rapid double antigen detection where the binding sites of the secondary antibodies are saturated by the specific primary immunoglobulins. This approach seems to avoid nonspecific binding of primary antibodies to Fc receptors, and the unwanted binding of secondary antibodies with cell surface immunoglobulins on B-lymphocytes or with crossreactive primary antibodies used in the other sequence, if the primary antibodies and the tissue are the same or crossreactive animal species.

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El-ghamry, Mosad A., Akila A. Saleh, Saied M. E. Khalil und Amira A. Mohammed. „Mono, bi- and trinuclear metal complexes derived from new benzene-1,4-bis(3-pyridin-2-ylurea) ligand. Spectral, magnetic, thermal and 3D molecular modeling studies“. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 110 (Juni 2013): 205–16. http://dx.doi.org/10.1016/j.saa.2013.03.016.

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Aguilar-Carrillo, Yovani, Lucía Soto-Urzúa, María De Los Ángeles Martínez-Martínez, Mirian Becerril-Ramírez und Luis Javier Martínez-Morales. „Computational Analysis of the Tripartite Interaction of Phasins (PhaP4 and 5)-Sigma Factor (σ24)-DNA of Azospirillum brasilense Sp7“. Polymers 16, Nr. 5 (23.02.2024): 611. http://dx.doi.org/10.3390/polym16050611.

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Azospirillum brasilense Sp7 produces PHB, which is covered by granule-associated proteins (GAPs). Phasins are the main GAPs. Previous studies have shown phasins can regulate PHB synthesis. When A. brasilense grows under stress conditions, it uses sigma factors to transcribe genes for survival. One of these factors is the σ24 factor. This study determined the possible interaction between phasins and the σ24 factor or phasin-σ24 factor complex and DNA. Three-dimensional structures of phasins and σ24 factor structures were predicted using the I-TASSER and SWISS-Model servers, respectively. Subsequently, a molecular docking between phasins and the σ24 factor was performed using the ClusPro 2.0 server, followed by molecular docking between protein complexes and DNA using the HDOCK server. Evaluation of the types of ligand–receptor interactions was performed using the BIOVIA Discovery Visualizer for three-dimensional diagrams, as well as the LigPlot server to obtain bi-dimensional diagrams. The results showed the phasins (Pha4Abs7 or Pha5Abs7)-σ24 factor complex was bound near the −35 box of the promoter region of the phaC gene. However, in the individual interaction of PhaP5Abs7 and the σ24 factor, with DNA, both proteins were bound to the −35 box. This did not occur with PhaP4Abs7, which was bound to the −10 box. This change could affect the transcription level of the phaC gene and possibly affect PHB synthesis.

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Jeffrey, Polly-Anne, Martín López-García, Mario Castro, Grant Lythe und Carmen Molina-París. „On Exact and Approximate Approaches for Stochastic Receptor-Ligand Competition Dynamics—An Ecological Perspective“. Mathematics 8, Nr. 6 (20.06.2020): 1014. http://dx.doi.org/10.3390/math8061014.

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Cellular receptors on the cell membrane can bind ligand molecules in the extra-cellular medium to form ligand-bound monomers. These interactions ultimately determine the fate of a cell through the resulting intra-cellular signalling cascades. Often, several receptor types can bind a shared ligand leading to the formation of different monomeric complexes, and in turn to competition for the common ligand. Here, we describe competition between two receptors which bind a common ligand in terms of a bi-variate stochastic process. The stochastic description is important to account for fluctuations in the number of molecules. Our interest is in computing two summary statistics—the steady-state distribution of the number of bound monomers and the time to reach a threshold number of monomers of a given kind. The matrix-analytic approach developed in this manuscript is exact, but becomes impractical as the number of molecules in the system increases. Thus, we present novel approximations which can work under low-to-moderate competition scenarios. Our results apply to systems with a larger number of population species (i.e., receptors) competing for a common resource (i.e., ligands), and to competition systems outside the area of molecular dynamics, such as Mathematical Ecology.

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