Journal articles: 'Ligand systems'

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Oszwałdowski, Sławomir, Katarzyna Zawistowska-Gibuła, and Kenneth Roberts. "Characterization of CdSe quantum dots with bidentate ligands by capillary electrophoresis." Open Chemistry 9, no. 4 (2011): 572–84. http://dx.doi.org/10.2478/s11532-011-0037-3.

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AbstractThe CdSe quantum dots (QDs) with bidentate ligands: a-diimine (NN) and dihydrolipoic acid (DHLA) were synthesized and characterized by UV-Vis, particle size and capillary electrophoretic techniques. Two systems were analyzed: CdSe with one ligand (CdSe/ligand) and CdSe with two different ligands (CdSe//ligand1/ligand2), where ligand = α-diimine or DHLA. Hydrodynamic features of functionalized QDs were characterized by zone capillary electrophoretic (CZE), and particle size techniques and these methods were consistent. It was established that CZE, micellar (MEKC) and microemulsion (MEEKC) modes were suitable for separating charged CdSe QDs and that no peaks were obtained for QDs passivated with electrically neutral ligands. For CdSe QDs with neutral (NN) ligands, a preconcentration method with the use of a micellar plug was introduced for visualizing these QDs. A sharp peak representing neutral QDs was obtained within the zone of micellar plug of a non-ionic surfactant, Here, a ligand character used for CdSe modification and the type of the electrophoretic method applied were the determining factors for the QDs peak visualization. Moreover, examples of visualization of charged and neutral QDs on the same run were presented, and for this purpose, dual mechanism (separation/preconcentration) was proposed.

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Ben-Shlomo, Izhar, Rami Rauch, Orna Avsian-Kretchmer, and Aaron J. W. Hsueh. "Matching Receptome Genes with Their Ligands for Surveying Paracrine/Autocrine Signaling Systems." Molecular Endocrinology 21, no. 8 (2007): 2009–14. http://dx.doi.org/10.1210/me.2007-0087.

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Abstract Sequencing of genomes from diverse organisms facilitates studies on the repertoire of genes involved in intercellular signaling. Extending previous efforts to annotate most human plasma membrane receptors in the Human Plasma Membrane Receptome database, we matched cognate ligands with individual receptors by surveying the published literature. In the updated online database we called “liganded receptome,” users can search for individual ligands or receptors to reveal their pairing partners and browse through receptor or ligand families to identify relationships between ligands and receptors in their respective families. Because local signaling systems are prevalent in diverse normal and diseased tissues, we used the liganded receptome knowledgebase to interrogate DNA microarray datasets for genome-wide analyses of potential paracrine/autocrine signaling systems. In addition to viewing ligand-receptor coexpression based on precomputed DNA microarray data, users can submit their own microarray data to perform online genome-wide searches for putative paracrine/autocrine signaling systems. Investigation of transcriptome data based on liganded receptome allows the discovery of paracrine/autocrine signaling for known ligand-receptor pairs in previously uncharacterized tissues or developmental stages. The present annotation of ligand-receptor pairs also identifies orphan receptors and ligands without known interacting partners in select families. Because hormonal ligands within the same family usually interact with paralogous receptors, this genomic approach could also facilitate matching of orphan receptors and ligands. The liganded receptome is accessible at http://receptome.stanford.edu.

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Zahid, Kanwal, Shazia Nisar, Saima Imad, Shazia Perveen, Shazia Ghaffar, and Nasreen Fatima. "Synthesis and Characterization of Homo and Mixed Ligand Complexes of Fe(III) with Hydroxypyridinone and Hydroxypyranone Type Ligands." Pakistan Journal of Scientific & Industrial Research Series A: Physical Sciences 63, no. 1 (2020): 12–17. http://dx.doi.org/10.52763/pjsir.phys.sci.63.1.2020.12.17.

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 Hydroxypyridinone and hydroxypyranone are known to be used for the treatment of iron overload by chelation therapy for a long time. Both the ligands have their own side effects when used as medicines. In the present study homo and mixed ligand complexes of both the ligands with iron were prepared and characterized by UV-visible spectrophotometry, Potentiometric study, IR spectroscopy, SEM/EDX and XRD. Overlay spectra obtained from UV-visible spectroscopy of our studied system show the formation of different types of species and confirm that mixed ligand complex is different from the other two systems. Potentiometric titration curves of homo and mixed ligand complexes show the formation of different types of species at different pH and confirm the formation of mixed ligand complex. The comparative results of SEM images of these systems show different surface topologies and hence conform to the formation of mixed ligand complex.

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Chen, Fang, Gangliang Huang, and Hualiang Huang. "Sugar ligand-mediated drug delivery." Future Medicinal Chemistry 12, no. 2 (2020): 161–71. http://dx.doi.org/10.4155/fmc-2019-0114.

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Sugar ligand molecules, such as mannose, galactose and glucose, can bind to drug-delivery systems, making them targeted. These glycosylation ligands have the advantages of nontoxicity, no immunogenicity, good biocompatibility and biodegradation. They can be widely used in glycosylation-modified drug-delivery systems. Herein, the targeting mechanisms, synthesis methods and targeting characteristics of glycosylation-modified drug-delivery systems were reviewed.

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Denizli, Adil, and Erhan Pişkin. "Dye-ligand affinity systems." Journal of Biochemical and Biophysical Methods 49, no. 1-3 (2001): 391–416. http://dx.doi.org/10.1016/s0165-022x(01)00209-3.

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Osguthorpe, D. J. "Modelling ligand-receptor systems." Neurochemistry International 21 (January 1992): S8. http://dx.doi.org/10.1016/0197-0186(92)91742-f.

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Wang, K. "Biological metal ligand systems." Pure and Applied Chemistry 60, no. 8 (1988): 1279–84. http://dx.doi.org/10.1351/pac198860081279.

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LIANG, G., and Q. YAO. "Ce 4f-LIGAND DEHYBRIDIZATION IN CeT2X2-BASED KONDO LATTICE/HEAVY FERMION SYSTEMS." International Journal of Modern Physics B 16, no. 19 (2002): 2815–22. http://dx.doi.org/10.1142/s0217979202011378.

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The lattice parameters of two CeT2X2 ( T =3d transition elements and X=Si and Ge) based Kondo lattice systems, the CeNi2-xCux Si2 and Ce(NiSi)2-x (CuGe)x, have been studied. The analysis of the Ce-ligand distances indicates that the variation of the a-parameter dominantly affects Ce 4f-X ligandn orbital hybridization whereas the variation of c-parameter dominantly affects Ce 4f-T ligand orbital hybridization. The average Ce-ligand distance varies linearly with x across the whole series in spite of the abnormal increase of the c-parameter in the region 1.6 ≤ x ≤ 2.0. Thus, our analysis shows that the average Ce 4f-ligand orbital hybridization decreases uniformly with x across the entire range of x for the CeNi2-xCuxSi 2 and Ce(NiSi)2-x(CuGe)x series. The means that the Ce 4f-ligand orbital dehybridization may not be a key factor to the formation of the heavy-fermion ground state in CeCu2Si2.

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M., Sivasankaran Nair, and Subbalakshmi G. "Multiple equilibria involved in some nickel(II) mixed ligand complex systems containing catecholic and dipeptide ligands." Journal of Indian Chemical Society Vol. 77, Jan 2000 (2000): 26–28. https://doi.org/10.5281/zenodo.5861391.

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Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627 012, India Manuscript received 10 February 1999, accepted 9 July 1999 Multiple equilibrium studies on NiII-dopamineklopa(A)-glycyl-L-tryosine and L-tyrosylglycine(B) systems show the formation of NiABH2, NiABH or NiAB mixed ligand complexes. The results indicate that dopa is ambidentate, i.e. in NiABH2 species it binds the metal ion in a glycine-like mode, while it coordinates in a pyrocatecholic mode in NiABH and NiAB complexes. Dopamine(A) binds in a pyrocatechol mode in its mixed ligand complexes. Both the dipeptide(B) ligands bind via N-amino and O-peptide groups in all the mixed ligand complexes.

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Martín-Mora, David, Matilde Fernández, Félix Velando, et al. "Functional Annotation of Bacterial Signal Transduction Systems: Progress and Challenges." International Journal of Molecular Sciences 19, no. 12 (2018): 3755. http://dx.doi.org/10.3390/ijms19123755.

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Bacteria possess a large number of signal transduction systems that sense and respond to different environmental cues. Most frequently these are transcriptional regulators, two-component systems and chemosensory pathways. A major bottleneck in the field of signal transduction is the lack of information on signal molecules that modulate the activity of the large majority of these systems. We review here the progress made in the functional annotation of sensor proteins using high-throughput ligand screening approaches of purified sensor proteins or individual ligand binding domains. In these assays, the alteration in protein thermal stability following ligand binding is monitored using Differential Scanning Fluorimetry. We illustrate on several examples how the identification of the sensor protein ligand has facilitated the elucidation of the molecular mechanism of the regulatory process. We will also discuss the use of virtual ligand screening approaches to identify sensor protein ligands. Both approaches have been successfully applied to functionally annotate a significant number of bacterial sensor proteins but can also be used to study proteins from other kingdoms. The major challenge consists in the study of sensor proteins that do not recognize signal molecules directly, but that are activated by signal molecule-loaded binding proteins.

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Goßen, Jonas, Rui Pedro Ribeiro, Dirk Bier, et al. "AI-based identification of therapeutic agents targeting GPCRs: introducing ligand type classifiers and systems biology." Chemical Science 14 (July 24, 2023): 8651–61. https://doi.org/10.5281/zenodo.8425842.

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Identifying ligands targeting G protein coupled receptors (GPCRs) with novel chemotypes other than the physiological ligands is a challenge for in silico screening campaigns. Here we present an approach that identifies novel chemotype ligands by combining structural data with a random forest agonist/antagonist classifier and a signal-transduction kinetic model. As a test case, we apply this approach to identify novel antagonists of the human adenosine transmembrane receptor type 2A, an attractive target against Parkinson's disease and cancer. The identified antagonists were tested here in a radio ligand binding assay. Among those, we found a promising ligand whose chemotype differs significantly from all so-far reported antagonists, with a binding affinity of 310 ± 23.4 nM. Thus, our protocol emerges as a powerful approach to identify promising ligand candidates with novel chemotypes while preserving antagonistic potential and affinity in the nanomolar range.

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M., Sivasankaran Nair, and A. Neelakantan M. "Solution behaviour of mixed ligand complexes of nickel(II) involving penicillin group drugs and sulfur containing ligands under physiological conditions." Journal of Indian Chemical Society Vol. 77, Aug 2000 (2000): 373–75. https://doi.org/10.5281/zenodo.5868329.

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Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627 012. India Department of Chemistry, National Engineering College, K. R. Nagar, Kovilpatti-628 503, India Munuscript received 22 March 2000. accetped 23 April 2000 Analysis of the pH-titration data obtained in aqueous perchlorate medium at 37° and I = 0.15 mol din-3 (NaCIO4) for Nill-A-B mixed ligand systems [A = 6apa or amp; B = cys, smc, pen or cya) shows the presence of mixed ligand complex species NiABH, NiAB and/or NiAB-1B in addition to various binary species due to ligands A and B. The \(pk_{NiABH}^{II}\) values obtained in all these systems are close to each other, indicating the site of protonation in the NiABH species to be with ligand A. In the NiAB type of complexes, coordination of the ligand A results in the formation of a five-membered ring. In the species in the Nill-amp(A)-B systems, deprotonated AH-1 ligand binds the metal in a tridentate manner. In all the mixed ligand complexes. cya, sine, pen and cya(B) ligands are bidentate. The statistical parameter ∆ log K calculated indicates preferential formation and enhanced stability for the mixed ligand complexes relative to the binary one.

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Pann, J., H. Roithmeyer, W. Viertl, et al. "Phosphines in artificial photosynthesis: considering different aspects such as chromophores, water reduction catalysts (WRCs), water oxidation catalysts (WOCs), and dyads." Sustainable Energy & Fuels 3, no. 11 (2019): 2926–53. http://dx.doi.org/10.1039/c9se00320g.

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Coordination complex systems containing phosphine ligands are used in artificial photosynthesis utilizing their unique stereoelectronic properties. Mono-, di- and tetraphosphines act as optimized ligand systems for complexation.

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Gorzsás, András, Ingegärd Andersson, and Lage Pettersson. "Speciation in aqueous vanadate–ligand and peroxovanadate–ligand systems." Journal of Inorganic Biochemistry 103, no. 4 (2009): 517–26. http://dx.doi.org/10.1016/j.jinorgbio.2008.12.006.

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15

Moreno, Maria João, Luís M. S. Loura, Jorge Martins, Armindo Salvador, and Adrian Velazquez-Campoy. "Analysis of the Equilibrium Distribution of Ligands in Heterogeneous Media–Approaches and Pitfalls." International Journal of Molecular Sciences 23, no. 17 (2022): 9757. http://dx.doi.org/10.3390/ijms23179757.

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The equilibrium distribution of small molecules (ligands) between binding agents in heterogeneous media is an important property that determines their activity. Heterogeneous systems containing proteins and lipid membranes are particularly relevant due to their prevalence in biological systems, and their importance to ligand distribution, which, in turn, is crucial to ligand’s availability and biological activity. In this work, we review several approaches and formalisms for the analysis of the equilibrium distribution of ligands in the presence of proteins, lipid membranes, or both. Special attention is given to common pitfalls in the analysis, with the establishment of the validity limits for the distinct approaches. Due to its widespread use, special attention is given to the characterization of ligand binding through the analysis of Stern–Volmer plots of protein fluorescence quenching. Systems of increasing complexity are considered, from proteins with single to multiple binding sites, from ligands interacting with proteins only to biomembranes containing lipid bilayers and membrane proteins. A new formalism is proposed, in which ligand binding is treated as a partition process, while considering the saturation of protein binding sites. This formalism is particularly useful for the characterization of interaction with membrane proteins.

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M., Sivasankaran Nair, and A. Neelakantan M. "Ternary complexes of nickel(II) involving ampicillin and some potentially bi- and tridentate ligands." Journal of Indian Chemical Society Vol. 77, Aug 2000 (2000): 394–96. https://doi.org/10.5281/zenodo.5868994.

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Department of Chemistry, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli-627 012, India Department of Chemistry, National Engineering College, K. R. Nagar, Kovilpatti-628 503. India Manuscript received 1 September 1999. revised 4 January 2000, accepted 1 April 2000 The multiple equilibrium studies involved in the NiII-ampicillin (amp)(A)-1,2-diaminopropane, 1,3-diaminopropane, DL,-2,3- diaminopropionic acid, DL-2,4-diaminobutyric acid and DL-2,5-diaminovaleric acid(B) systems show the presence of NiABH2, NiABH. NiAB and NiABH-1 ternary species. In the NiABH2 species one proton is attached with ligand (A) and the other with ligand (B), while in the NiABH species the site of protonation is ligand (B). In the NiABH-1 species the deprotonation occurs with ligand (A). In all these systems, in the NiAB species the binding of the ligands A and B is similar to their binding in their respectile binary systems.

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Davis, Carol A., Jeong Kim, Leonard F. Lindoy, Seong-Hwa Lee, and Anthony J. Leong. "Macrocyclic Ligand Design. Structure - Function Relationships Underlying the Interaction of Zinc(II), Cadmium(II), Silver(I) and Lead(II) with Mixed-Donor Macrocyclic Ligands." Australian Journal of Chemistry 51, no. 3 (1998): 189. http://dx.doi.org/10.1071/c97188.

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An investigation of the interaction of zinc(II), cadmium(II), silver(I) and lead(II) with a series of mixed-donor dibenzo-substituted macrocyclic ligands, incorporating O2N3-, O2N4-, O3N2-, O3N3-, O4N2- and O2N3S-donor sets, has been carried out. The log K values for the respective complexes in 95% methanol (I = 0·1; Et4NClO4, 25°C) have been determined potentiometrically. All ligands form 1 : 1 (metal/ligand) complexes with the above metal ions although in isolated cases species of type MLH2+ were also observed. An investigation of the effect of variation of ligand structure on the respective complex stabilities has been carried out and the results compared with those obtained previously for closely related mixed-donor macrocyclic systems. The binding of silver(I) and lead(II) to the 17- and 18-membered O3N2-ligand systems has been assessed in (CD3)2SO by means of 13C n.m.r. spin–lattice relaxation (T1) studies as well as by observation of the induced chemical shifts of particular ligand resonances on complex formation. Overall, the n.m.r. results correlate well with the observed thermodynamic stabilities of the individual complexes.

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Jiménez-Pérez, Alondra, Sara Marcos-Gómez, Gotzon Madariaga, et al. "Thiosemicarbazonecopper/Halido Systems: Structure and DFT Analysis of the Magnetic Coupling." Inorganics 11, no. 1 (2023): 31. http://dx.doi.org/10.3390/inorganics11010031.

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Experimental magnetic studies performed on the [{CuLX}2] system (HL = pyridine-2-carbaldehyde thiosemicarbazone, X = Cl−, Br−, I−) point to the larger electronegativity in X, the lower magnitude of the antiferromagnetic interactions. In order to confirm this and other trends observed and to dip into them, computational studies on the [{CuLX}2] (X = Cl− (1), I− (2)) compounds are here reported. The chemical and structural comparisons have been extended to the compounds obtained in acid medium. In this regard, chlorido ligands yield the [Cu(HL)Cl2]∙H2O (3) complex, whose crystal structure shows that thiosemicarbazone links as a tridentate chelate ligand to square pyramidal Cu(II) ions. On the other hand, iodido ligands provoke the formation of the [{Cu(H2L)I2}2] (4) derivative, which contains pyridine-protonated cationic H2L+ as a S-donor monodentate ligand bonded to Cu(I) ions. Crystallographic, infrared and electron paramagnetic resonance spectroscopic results are discussed. Computational calculations predict a greater stability for the chlorido species, containing both the neutral (HL) and anionic (L−) ligand. The theoretical magnetic studies considering isolated dimeric entities reproduce the sign and magnitude of the antiferromagnetism in 1, but no good agreement is found for compound 2. The sensitivity to the basis set and the presence of interdimer magnetic interactions are debated.

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Ferrer, E. G., P. A. M. Williams, and E. J. Baran. "Interaction of the Vanadyl(IV) Cation with L-Ascorbic Acid and Related Systems." Zeitschrift für Naturforschung B 53, no. 2 (1998): 256–62. http://dx.doi.org/10.1515/znb-1998-0220.

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Abstract The interaction of VO2+ with L-ascorbic acid and dehydroascorbic acid was investigated by electronic spectroscopy in solution at different pH values. In the case of ascorbic acid, two different solid complexes containing one or two monodeprotonated ascorbate ligands could be isolated and characterized. With dehydroascorbic acid, interaction begins at pH = 4 but at higher pH values the ligand is hydrolysed irreversibly, generating 2,3-diketogulonic acid. A solid complex containing this ligand could be precipitated at pH = 7. Its spectroscopic behavior confirms the interaction of the cation with an enolised form of the acid.

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Li, Long, Yudie Zhang, and Jizeng Wang. "Effects of ligand distribution on receptor-diffusion-mediated cellular uptake of nanoparticles." Royal Society Open Science 4, no. 5 (2017): 170063. http://dx.doi.org/10.1098/rsos.170063.

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Biophysical-factor-dependent cellular uptake of nanoparticles (NPs) through receptor-diffusion-mediated endocytosis bears significance in pathology, cellular immunity and drug-delivery systems. Advanced nanotechnology of NP synthesis provides methods for modifying NP surface with different ligand distributions. However, no report discusses effects of ligand distribution on NP surface on receptor-diffusion-mediated cellular uptake. In this article, we used a statistical dynamics model of receptor-diffusion-mediated endocytosis to examine ligand-distribution-dependent cellular uptake dynamics by considering that ligand–receptor complexes drive engulfing to overcome resistance to membrane deformation and changes in configuration entropy of receptors. Results showed that cellular internalization of NPs strongly depended on ligand distribution and that cellular-uptake efficiency of NPs was high when ligand distribution was within a range around uniform distribution. This feature of endocytosis ensures robust infection ability of viruses to enter host cells. Interestingly, results also indicated that optimal ligand distribution associated with highest cellular-uptake efficiency slightly depends on distribution pattern of ligands and density of receptors, and the optimal distribution becomes uniform when receptor density is sufficiently large. Position of initial contact point is also a factor affecting dynamic wrapping. This study explains why most enveloped viruses present almost homogeneous ligand distribution and is useful in designing controlled-release drug-delivery systems.

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Jones, Dafydd D. L., Samuel Watts та Cameron Jones. "Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes". Inorganics 9, № 9 (2021): 72. http://dx.doi.org/10.3390/inorganics9090072.

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Sterically bulky β-diketiminate (or Nacnac) ligand systems have recently shown the ability to kinetically stabilize highly reactive low-oxidation state main group complexes. Metal halide precursors to such systems can be formed via salt metathesis reactions involving alkali metal complexes of these large ligand frameworks. Herein, we report the synthesis and characterization of lithium and potassium complexes of the super bulky anionic β-diketiminate ligands, known [TCHPNacnac]− and new [TCHP/DipNacnac]− (ArNacnac = [(ArNCMe)2CH]−) (Ar = 2,4,6-tricyclohexylphenyl (TCHP) or 2,6-diisopropylphenyl (Dip)). The reaction of the proteo-ligands, ArNacnacH, with nBuLi give the lithium etherate compounds, [(TCHPNacnac)Li(OEt2)] and [(TCHP/DipNacnac)Li(OEt2)], which were isolated and characterized by multinuclear NMR spectroscopy and X-ray crystallography. The unsolvated potassium salts, [{K(TCHPNacnac)}2] and [{K(TCHP/DipNacnac)}∞], were also synthesized and characterized in solution by NMR spectroscopy. In the solid state, these highly reactive potassium complexes exhibit differing alkali metal coordination modes, depending on the ligand involved. These group 1 complexes have potential as reagents for the transfer of the bulky ligand fragments to metal halides, and for the subsequent stabilization of low-oxidation state metal complexes.

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Leng, Qixin, Martin C. Woodle, and A. James Mixson. "Targeted Delivery of siRNA Therapeutics to Malignant Tumors." Journal of Drug Delivery 2017 (November 9, 2017): 1–22. http://dx.doi.org/10.1155/2017/6971297.

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Over the past 20 years, a diverse group of ligands targeting surface biomarkers or receptors has been identified with several investigated to target siRNA to tumors. Many approaches to developing tumor-homing peptides, RNA and DNA aptamers, and single-chain variable fragment antibodies by using phage display, in vitro evolution, and recombinant antibody methods could not have been imagined by researchers in the 1980s. Despite these many scientific advances, there is no reason to expect that the ligand field will not continue to evolve. From development of ligands based on novel or existing biomarkers to linking ligands to drugs and gene and antisense delivery systems, several fields have coalesced to facilitate ligand-directed siRNA therapeutics. In this review, we discuss the major categories of ligand-targeted siRNA therapeutics for tumors, as well as the different strategies to identify new ligands.

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Borówko, Małgorzata, and Tomasz Staszewski. "Adsorption on Ligand-Tethered Nanoparticles." International Journal of Molecular Sciences 22, no. 16 (2021): 8810. http://dx.doi.org/10.3390/ijms22168810.

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We use coarse-grained molecular dynamics simulations to study adsorption on ligand-tethered particles. Nanoparticles with attached flexible and stiff ligands are considered. We discuss how the excess adsorption isotherm, the thickness of the polymer corona, and its morphology depend on the number of ligands, their length, the size of the core, and the interaction parameters. We investigate the adsorption-induced structural transitions of polymer coatings. The behavior of systems involving curved and flat “brushes” is compared.

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Zia, Adil, Yuao Wu, Tuan Nguyen, Xiaowei Wang, Karlheinz Peter, and Hang T. Ta. "The choice of targets and ligands for site-specific delivery of nanomedicine to atherosclerosis." Cardiovascular Research 116, no. 13 (2020): 2055–68. http://dx.doi.org/10.1093/cvr/cvaa047.

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Abstract As nanotechnologies advance into clinical medicine, novel methods for applying nanomedicine to cardiovascular diseases are emerging. Extensive research has been undertaken to unlock the complex pathogenesis of atherosclerosis. However, this complexity presents challenges to develop effective imaging and therapeutic modalities for early diagnosis and acute intervention. The choice of ligand-receptor system vastly influences the effectiveness of nanomedicine. This review collates current ligand-receptor systems used in targeting functionalized nanoparticles for diagnosis and treatment of atherosclerosis. Our focus is on the binding affinity and selectivity of ligand-receptor systems, as well as the relative abundance of targets throughout the development and progression of atherosclerosis. Antibody-based targeting systems are currently the most commonly researched due to their high binding affinities when compared with other ligands, such as antibody fragments, peptides, and other small molecules. However, antibodies tend to be immunogenic due to their size. Engineering antibody fragments can address this issue but will compromise their binding affinity. Peptides are promising ligands due to their synthetic flexibility and low production costs. Alongside the aforementioned binding affinity of ligands, the choice of target and its abundance throughout distinct stages of atherosclerosis and thrombosis is relevant to the intended purpose of the nanomedicine. Further studies to investigate the components of atherosclerotic plaques are required as their cellular and molecular profile shifts over time.

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Marsh, Lorraine. "Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites." BioMed Research International 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/746980.

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Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorableΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorableΔGbecause of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total bindingΔGarising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where “nonspecific” interactions contribute to biological function.

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Seema, Kumari Yadav, Upadhayaya (Dwivedi) Neerja, Nair (Ahuja) R., and Dwivedi K. "Solution study of ternary systems involving transition metals, dipeptide and catecholic ligands." Journal of Indian Chemical Society Vol. 88, Oct 2011 (2011): 1599–603. https://doi.org/10.5281/zenodo.5790685.

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School of Studies in Chemistry, Jiwaji University, Gwalior-474 011, Madhya Pradesh, India E-mail: seema_chem@rediffmail.com vijaya Raje Govt. Girls P.G. College, Morar, Gwalior, Madhya Pradesh, India Manuscript received 08 June 2010, revised 08 March 2011, accepted 09 March 2011 Glycylglycine (Giygly), L-3,4-dihydroxyphenylalanine (DOPA) and L-tyrosine (Tyr) are three important ligands in biological systems. In order to draw inference on their complexation behaviour, solution studies in mixed ligand systems involving these ligands with NiII, CoII and CdII have been carried using pH-metric titration technique, in aqueous medium at three different Ionic strengths (μ. =0.05, 0.10, 0.15 M) and at two different temperatures 20°C and 30°C. SCOGS computer program was applied for computation. Protonated and non-protonated mixed ligand complexes are inferred to be formed through multiple equilibria. Distribution of various species is presented in the form of speciation curves. The two ligands are coordinated to the metal ion simultaneously in a single step. Δ log K values support the formation of ternary complexes.

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Williams, Mobolaji. "Derangement model of ligand-receptor binding." Computational and Mathematical Biophysics 10, no. 1 (2022): 123–66. http://dx.doi.org/10.1515/cmb-2022-0137.

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Abstract We introduce a derangement model of ligand-receptor binding that allows us to quantitatively frame the question “How can ligands seek out and bind to their optimal receptor sites in a sea of other competing ligands and suboptimal receptor sites?” To answer the question, we first derive a formula to count the number of partial generalized derangements in a list, thus extending the derangement result of Gillis and Even. We then compute the general partition function for the ligand-receptor system and derive the equilibrium expressions for the average number of bound ligands and the average number of optimally bound ligands. A visual model of squares assembling onto a grid allows us to easily identify fully optimal bound states. Equilibrium simulations of the system reveal its extremes to be one of two types, qualitatively distinguished by whether optimal ligand-receptor binding is the dominant form of binding at all temperatures and quantitatively distinguished by the relative values of two critical temperatures. One of those system types (termed “search-limited,” as it was in previous work) does not exhibit kinetic traps and we thus infer that biomolecular systems where optimal ligand-receptor binding is functionally important are likely to be search-limited.

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Pieroni, Michele, Francesco Madeddu, Jessica Di Martino, et al. "MD–Ligand–Receptor: A High-Performance Computing Tool for Characterizing Ligand–Receptor Binding Interactions in Molecular Dynamics Trajectories." International Journal of Molecular Sciences 24, no. 14 (2023): 11671. http://dx.doi.org/10.3390/ijms241411671.

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Molecular dynamics simulation is a widely employed computational technique for studying the dynamic behavior of molecular systems over time. By simulating macromolecular biological systems consisting of a drug, a receptor and a solvated environment with thousands of water molecules, MD allows for realistic ligand–receptor binding interactions (lrbi) to be studied. In this study, we present MD–ligand–receptor (MDLR), a state-of-the-art software designed to explore the intricate interactions between ligands and receptors over time using molecular dynamics trajectories. Unlike traditional static analysis tools, MDLR goes beyond simply taking a snapshot of ligand–receptor binding interactions (lrbi), uncovering long-lasting molecular interactions and predicting the time-dependent inhibitory activity of specific drugs. With MDLR, researchers can gain insights into the dynamic behavior of complex ligand–receptor systems. Our pipeline is optimized for high-performance computing, capable of efficiently processing vast molecular dynamics trajectories on multicore Linux servers or even multinode HPC clusters. In the latter case, MDLR allows the user to analyze large trajectories in a very short time. To facilitate the exploration and visualization of lrbi, we provide an intuitive Python notebook (Jupyter), which allows users to examine and interpret the results through various graphical representations.

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Yang, Dongdong, Xiaxia Liu, Liping Lu, and Miaoli Zhu. "Effects of two different solvents on the syntheses, structural diversity, and magnetic properties of six Mn(ii) complexes derived from 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoate and variable N-donor ligands." CrystEngComm 22, no. 46 (2020): 8088–99. http://dx.doi.org/10.1039/d0ce01383h.

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Six Mn(ii) complexes of the 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoate ligand in two different solvent systems with variable N-donor ligands were obtained and showed different structures and magnetic properties.

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30

Caspers, Nicole L., Seungil Han, Francis Rajamohan, et al. "Development of a high-throughput crystal structure-determination platform for JAK1 using a novel metal-chelator soaking system." Acta Crystallographica Section F Structural Biology Communications 72, no. 11 (2016): 840–45. http://dx.doi.org/10.1107/s2053230x16016356.

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Crystals of phosphorylated JAK1 kinase domain were initially generated in complex with nucleotide (ADP) and magnesium. The tightly bound Mg2+-ADP at the ATP-binding site proved recalcitrant to ligand displacement. Addition of a molar excess of EDTA helped to dislodge the divalent metal ion, promoting the release of ADP and allowing facile exchange with ATP-competitive small-molecule ligands. Many kinases require the presence of a stabilizing ligand in the ATP site for crystallization. This procedure could be useful for developing co-crystallization systems with an exchangeable ligand to enable structure-based drug design of other protein kinases.

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Jeffrey, Polly-Anne, Martín López-García, Mario Castro, Grant Lythe, and Carmen Molina-París. "On Exact and Approximate Approaches for Stochastic Receptor-Ligand Competition Dynamics—An Ecological Perspective." Mathematics 8, no. 6 (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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32

Oldenhof, Sander, Martin Lutz, Bas de Bruin, Jarl Ivar van der Vlugt, and Joost N. H. Reek. "Dehydrogenation of formic acid by Ir–bisMETAMORPhos complexes: experimental and computational insight into the role of a cooperative ligand." Chemical Science 6, no. 2 (2015): 1027–34. http://dx.doi.org/10.1039/c4sc02555e.

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The synthesis of Ir-complexes with three bisMETAMORPhos ligands is reported. The activity of these systems towards HCOOH dehydrogenation and the dual role of the ligand during catalysis is discussed, using spectroscopic and computational methods.

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33

Biswas, Arpita. "A Brief Review on Homo-/Hetero-nuclear Co-ordination Compounds Derived from Some Single Compartmentl Acyclic Schiff Base Ligands having N-,O-Donor Centres." Oriental Journal Of Chemistry 38, no. 4 (2022): 957–66. http://dx.doi.org/10.13005/ojc/380417.

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Tetradentate acyclic compartmental Schiff base ligand with N2O2 compartment afford suitable coordination environment for large variety of metal ions. This type of ligands can easily be synthesized by [2+1] condensation of a carbonyl compounds with a diamine. Several metal complexes have been reported from the single- and double-compartment acyclic Schiff base ligands which are the [2+1] condensation products of salicylaldehyde, 2-hydroxyacetophenone, 3-methoxysalicylaldehyde, 3-ethoxysalicylaldehyde and a diamine; The diamine counterpart in these ligands are ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1-methylethylenediamine, 2,2-dimethyl,1,3-diaminopropane, o-phenylenediamine, trans-1,2-diaminocyclohexane, etc. Several review article has been published previously on compartmental Schiff base ligand compounds. This review article focused only the type and structures of Cu(II)/Ni(II)-second metal (s-, p-, d10-, 3d-,, 4f- block metal) homo-/hetero- nuclear coordination comppounds derived from single compartmentl salicyaldehyde-diamine and acetophenone-diamine ligand systems.

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34

Li, Peiyi, Birte Ahrens, Ka-Ho Choi, et al. "Metal–metal and ligand–ligand interactions in gold poly-yne systems." CrystEngComm 4, no. 69 (2002): 405–12. http://dx.doi.org/10.1039/b202283d.

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35

Chernova, R. K., and S. N. Shtykov. "Hydrophobic ligand-ligand interactions in multicomponent systems and their analytical significance." Fresenius' Zeitschrift für analytische Chemie 335, no. 1 (1989): 111–16. http://dx.doi.org/10.1007/bf00482402.

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36

Shave, S. R., P. Taylor, M. Walkinshaw, L. Smith, J. Hardy, and A. Trew. "Ligand discovery on massively parallel systems." IBM Journal of Research and Development 52, no. 1.2 (2008): 57–67. http://dx.doi.org/10.1147/rd.521.0057.

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Kuzu, Istemi, Ivo Krummenacher, Jens Meyer, Felix Armbruster, and Frank Breher. "Multidentate ligand systems featuring dual functionality." Dalton Transactions, no. 43 (2008): 5836. http://dx.doi.org/10.1039/b808347a.

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Vogler, Arnd, and Horst Kunkely. "Optical Ligand to Ligand Charge Transfer of Metal Complexes Including Ligand-Based Mixed-Valence Systems." Comments on Inorganic Chemistry 9, no. 3-4 (1990): 201–20. http://dx.doi.org/10.1080/02603599008035810.

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39

Walser, Reto, Jörg H. Kleinschmidt, Arne Skerra та Oliver Zerbe. "β-Barrel scaffolds for the grafting of extracellular loops from G-protein-coupled receptors". Biological Chemistry 393, № 11 (2012): 1341–55. http://dx.doi.org/10.1515/hsz-2012-0234.

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Abstract Owing to the difficulties in production and purification of G-protein-coupled receptors (GPCRs), relatively little structural information is available about this class of receptors. Here we aim at developing small chimeric proteins, displaying the extracellular ligand-binding motifs of a human GPCR, the Y receptor. This allows the study of ligand-receptor interactions in simplified systems. We present comprehensive information on the use of transmembrane (OmpA) and soluble (Blc) β-barrel scaffolds. Whereas Blc appeared to be not fully compatible with our approach, owing to problems with refolding of the hybrid constructs, loop-grafted versions of OmpA delivered encouraging results. Previously, we described a chimeric construct based on OmpA displaying all three extracellular Y1 receptor loops in different topologies and showing moderate affinity to one of the natural ligands. Now, we present detailed data on the interaction of these constructs with several Y receptor ligands along with data on new constructs. Our findings suggest a common binding mode for all ligands, which is mediated through the C-terminal residues of the peptide ligand, supporting the functional validity of these hybrid receptors. The observed binding affinities, however, are well below those observed for the natural receptors, clearly indicating limitations in mimicking the natural systems.

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40

K., Hussain Reddy, and Sambasiva Reddy P. "Synthesis and spectral characterization of mixed ligand zinc(II) complexes with heteroaromatic thiosemicarbazones and pyridine/picoline." Journal of Indian Chemical Society Vol. 79, Feb 2002 (2002): 132–34. https://doi.org/10.5281/zenodo.5841022.

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Department of Chemistry, Sri Krishnadevaraya University, Anantapur-515 003, India Fax : 91-08554-29043 Manuscript received 14 September 2000, revised 3 July 2001, accepted 14 July 2001 Mixed ligand complexes of zinc(n) with thiocarbamic acid [(thiophene-2-yl)methylene]hydrazide (TTMH) and thiocarbamic acid [(thiophene-2-yl)ethylideneThydrazide (TTEH) as primary ligands and pyridine (py) and 4-picoline (pie) as secondary ligands have been prepared. The primary ligands act as bidentate ligands in all the zinc complexes. The parent compounds, [Zn(TTMH)C12] and [Zn(TTEH)C12] are found to be four-coordinate zinc complexes. Octahedral geometry is assigned for the mixed ligand zinc(n) complexes with TTMH/TTEH and pyridine/picoline.

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41

Mierke, Dale F., and Maria Pellegrini. "Parathyroid Hormone and Parathyroid Hormone-Related Protein: Model Systems for the Development of an Osteoporosis Therapy." Current Pharmaceutical Design 5, no. 1 (1999): 21–36. http://dx.doi.org/10.2174/1381612805666230109195250.

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The parathyroid hormone (PTH) plays a vital role in the homeostasis of calcium within the blood stream. Given its unique ability to increase bone density, an understanding of the molecular mechanism by which the hormone is recognized and binds to its receptor should provide targets for the development of PTH based, anabolic agents for the treatment of osteoporosis. Parathyroid hormone related protein (PTHrP), a genetically and structurally distinct hormone which displays similar binding and activation profiles as PTH, has greatly facilitated the effort to establish a structure-biological function relationship by allowing for direct comparisons. In an analogous manner, the presence of two receptors, PTH/PTHrP (PTHl) and PTH2, which differ in their ligand selectivity (PTH2 is activated by PTH, not PTHrP) has provided a unique vehicle for probing the structural motifs of the receptor required for ligand recognition and binding. Recent photo-affinity cross-linking studies of PTH and PTHrP binding to PTHI have produced direct points of contact between the ligand and receptor. Here, we review each of the components involved in this important hormone system, with particular emphasis on the structural features of each: the ligands (PTH and PTHrP), the receptors (PTHl and PTH2), and the interaction between ligand and receptor. Although the current understanding of the molecular mechanism of ligand binding and receptor activation does not allow for the rational design of drug candidates, and indeed contains much conjecture, significant strides have been made towards this end.

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42

Cavell, KJ. "Metal Chelate Systems as Catalysts for Olefin and Carbon Monoxide Conversion Reactions." Australian Journal of Chemistry 47, no. 5 (1994): 769. http://dx.doi.org/10.1071/ch9940769.

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The application of non-phosphine-based chelating ligands in homogeneous catalyst systems is a surprisingly recent and relatively unexplored area of research. Chelating ligands can concurrently stabilize intermediates, control catalyst activity and direct the product distribution far more effectively than monodentate ligands. In this review our studies with catalyst systems containing chelate ligands primarily of the β-diketonate type [dithio-β-diketonate (sacsac); monothio-β-diketonate (sacac); and imino β-diketonate (nacac) ligands] is discussed. Examples of the catalyst systems show enzyme-like superactivity. Studies modelling these catalyst systems have provided valuable information relating the effects of ligand modifications to reaction pathways and to activities. Our most recent investigations of simple chelating ligands based on picolinic acid are also discussed. Studies modelling CO/ethene insertion/elimination with extremely labile alkylplatinum picolinate complexes led to the development of new single-component nickel oligomerization catalysts.

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Gipson, Kyle, Brett Ellerbrock, Kathryn Stevens, Phil Brown, and John Ballato. "Light-Emitting Polymer Nanocomposites." Journal of Nanotechnology 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/386503.

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Inorganic nanoparticles doped with optically active rare-earth ions and coated with organic ligands were synthesized in order to create fluorescent polymethyl methacrylate (PMMA) nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were utilized in order to functionalize the surface of Tb3+ : LaF3nanocrystals. The selected aromatic ligand systems were characterized using infrared spectroscopy, thermal analysis, rheological measurements, and optical spectroscopy. Nanoparticles producedin situwith the PMMA contained on average 10 wt% loading of Tb3+ : LaF3at a 6 : 1 La : Tb molar ratio and ~7 wt% loading of 4 : 1 La : Tb molar ratio for the PA and ASA systems, respectively. Measured diameters ranged from457±176 nm to150±105 nm which is indicative that agglomerates formed during the synthesis process. Both nanocomposites exhibited the characteristic Tb3+emission peaks upon direct ion excitation (350 nm) and ligand excitation (PA : 265 nm and ASA : 275 nm).

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44

Martin, Stephen F. "Preorganization in biological systems: Are conformational constraints worth the energy?" Pure and Applied Chemistry 79, no. 2 (2007): 193–200. http://dx.doi.org/10.1351/pac200779020193.

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It is generally assumed that preorganizing a flexible ligand in the three-dimensional shape it adopts when bound to a macromolecular receptor will provide a derivative having an increased binding affinity, primarily because the rigidified molecule is expected to benefit from a lesser entropic penalty during complexation. We now provide the first experimental evidence that demonstrates this common belief is not universally true. Indeed, we find that ligand preorganization may be accompanied by an unfavorable entropy of binding, even when the constrained ligand exhibits a higher binding affinity than its flexible control. Thus, the effects that ligand preorganization have upon energetics and structure in protein-ligand interactions must be reevaluated.

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Paulmurugan, Ramasamy, Anobel Tamrazi, John A. Katzenellenbogen, Benita S. Katzenellenbogen та Sanjiv S. Gambhir. "A Human Estrogen Receptor (ER)α Mutation with Differential Responsiveness to Nonsteroidal Ligands: Novel Approaches for Studying Mechanism of ER Action". Molecular Endocrinology 22, № 7 (2008): 1552–64. http://dx.doi.org/10.1210/me.2007-0570.

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Abstract Estrogens, acting through the estrogen receptors (ERs), play crucial roles in regulating the function of reproductive and other systems under physiological and pathological conditions. ER activity in regulating target genes is modulated by the binding of both steroidal and synthetic nonsteroidal ligands, with ligand binding inducing ERs to adopt various conformations that control their interactions with transcriptional coregulators. Previously, we developed an intramolecular folding sensor with a mutant form of ERα (ERG521T) that proved to be essentially unresponsive to the endogenous ligand 17β-estradiol, yet responded very well to certain synthetic ligands. In this study, we have characterized this G521T-ER mutation in terms of the potency and efficacy of receptor response toward several steroidal and nonsteroidal ligands in two different ways: directly, by ligand effects on mutant ER conformation (by the split-luciferase complementation system), and indirectly, by ligand effects on mutant ER transactivation. Full-length G521T-ER shows no affinity for estradiol and does not activate an estrogen-responsive reporter gene. The synthetic pyrazole agonist ligand propyl-pyrazole-triol is approximately 100-fold more potent than estradiol in inducing intramolecular folding and reporter gene transactivation with the mutant ER, whereas both ligands have high potency on wild-type ER. This estradiol-unresponsive mutant ER can also specifically highlight the agonistic property of the selective ER modulator, 4-hydroxytamoxifen, by reporter gene transactivation, even in the presence of estradiol, and it can exert a dominant-negative effect on estrogen-stimulated wild-type ER. This system provides a model for ER-mutants that show differential ligand responsiveness to gene activation to gain insight into the phenomenon of hormone resistance observed in endocrine therapies of ER-positive breast cancers.

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Duchardt-Ferner, Elke, Michael Juen, Benjamin Bourgeois, et al. "Structure of an RNA aptamer in complex with the fluorophore tetramethylrhodamine." Nucleic Acids Research 48, no. 2 (2019): 949–61. http://dx.doi.org/10.1093/nar/gkz1113.

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Abstract RNA aptamers—artificially created RNAs with high affinity and selectivity for their target ligand generated from random sequence pools—are versatile tools in the fields of biotechnology and medicine. On a more fundamental level, they also further our general understanding of RNA-ligand interactions e. g. in regard to the relationship between structural complexity and ligand affinity and specificity, RNA structure and RNA folding. Detailed structural knowledge on a wide range of aptamer–ligand complexes is required to further our understanding of RNA–ligand interactions. Here, we present the atomic resolution structure of an RNA–aptamer binding to the fluorescent xanthene dye tetramethylrhodamine. The high resolution structure, solved by NMR-spectroscopy in solution, reveals binding features both common and different from the binding mode of other aptamers with affinity for ligands carrying planar aromatic ring systems such as the malachite green aptamer which binds to the tetramethylrhodamine related dye malachite green or the flavin mononucleotide aptamer.

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47

Throckmorton, Linda, and Dennis S. Marynick. "Ligand exchange in (.eta.5-cyclopentadienyl)nickel ligand systems: a theoretical study." Journal of Physical Chemistry 92, no. 3 (1988): 645–50. http://dx.doi.org/10.1021/j100314a016.

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48

Chen, Cheng, Yang Miao, Kimmy De Winter, et al. "Ruthenium-Based Catalytic Systems Incorporating a Labile Cyclooctadiene Ligand with N-Heterocyclic Carbene Precursors for the Atom-Economic Alcohol Amidation Using Amines." Molecules 23, no. 10 (2018): 2413. http://dx.doi.org/10.3390/molecules23102413.

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Transition-metal-catalyzed amide-bond formation from alcohols and amines is an atom-economic and eco-friendly route. Herein, we identified a highly active in situ N-heterocyclic carbene (NHC)/ruthenium (Ru) catalytic system for this amide synthesis. Various substrates, including sterically hindered ones, could be directly transformed into the corresponding amides with the catalyst loading as low as 0.25 mol.%. In this system, we replaced the p-cymene ligand of the Ru source with a relatively labile cyclooctadiene (cod) ligand so as to more efficiently obtain the corresponding poly-carbene Ru species. Expectedly, the weaker cod ligand could be more easily substituted with multiple mono-NHC ligands. Further high-resolution mass spectrometry (HRMS) analyses revealed that two tetra-carbene complexes were probably generated from the in situ catalytic system.

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Zarate, Ximena, Eduardo Schott, Emilio Bunel, Juan M. Manríquez, and Ivonne Chávez. "Study of the Molecular Properties of Mono- and Binuclear Metal s-Indacenyl Complexes with Ir, Rh, and Re: A Theoretical Approach." Journal of Chemistry 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/9101720.

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Density functional theory (DFT) calculations were performed on a new family of mono- and bimetallic complexes, containing 4,8-([10]paracyclophane)-1,5-dihydro-s-indacene as the bridging ligand between the two metallic centers and different ancillary ligands. The s-indacene was blocked by substitution of the central benzene ring with the [10]paracyclophane to obtain the syn-conformations. This would force the metallic centers to be close together. It is proposed, due to the calculated molecular and electronic properties such as the reactivity indexes, the delocalized nature of the s-indacenyl ligand, and the electron-rich metals, that these systems could be reactive in a catalytic reaction. The results indicate that the systems with Rh and Re holding ancillary ligands such as bipy and CO show the best properties to be active in a chemical reaction. In this sense, by the assessed geometrical and electronic properties, when compared with a previously reported system, these complexes could be candidates for the reduction of CO2 to oxalate.

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Kapustian, A., and N. Cherno. "Determination of complex forming ability of mixed-ligand organic systems relative to the metal ions." Scientific Messenger of LNU of Veterinary Medicine and Biotechnologies 21, no. 91 (2019): 130–35. http://dx.doi.org/10.32718/nvlvet-f9122.

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It is shown that classical and specific methods for determining the complex forming ability of mixed-ligand organic systems relative to the metal ions is not perfect. Determination of complex-forming ability of mixed-ligand organic systems relative to the metal ions using the method of turbidimetry for media containing biometal chlorides, mixed-ligand systems and sodium carbonate is proposed. As mixed-ligand systems used the culture fluid Bifidobacterium bifidum AC-1670 (mixed-ligand system I), the culture fluid of the composition of probiotic bacteria (mixed-ligand system II), the culture fluid of the composition of probiotic bacteria with the introduction of exogenous chelating agents (mixed-ligand system III), culture fluid of probiotic bacteria composition and products of their cell walls processing (mixed-ligand system IV). A solution of metal chloride (magnesium or calcium, or cuprum, or manganese, or ferrum or zinc) was added discretely to the aliquots of the solution of the organic mixed-ligand system. The mixture was stirred and kept for 30 minutes at 40 °C, then a solution of sodium carbonate was added to the aliquots and discretely measured turbidity of the solution by turbidimetric method at a wavelength of 450 nm. When the increasing of the turbidity magnitude system by 0.02 opt. un, a conclusion about the maximum value of the mixed-ligand organic systems complex forming capacity relative to the metal ion was made. Further increase in the turbidity of the system indicates an increase in the metal content in inorganic form, respectively the complex formation potential of the mixed-ligand system is exhausted. It is determined that the highest complex forming ability in relation to ions of biometals has mixed-ligand system III. The proposed method allows precisely to determine the complex formation capacity of mixed-ligand organic systems in relation to metal ions without the use of aggressive reagents capable of destroying chelate bonds and without involving high-cost rare equipment.

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Journal articles on the topic 'Ligand systems'

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