scholarly journals Roles of Organic Fragments in Redirecting Crystal/Molecular Structures of Inorganic–Organic Hybrids Based on Lacunary Keggin-Type Polyoxometalates

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5994
Author(s):  
Ruhollah Khajavian ◽  
Vida Jodaian ◽  
Fatemeh Taghipour ◽  
Joel T. Mague ◽  
Masoud Mirzaei
Keyword(s):  
Organic Ligand ◽  
Molecular Structures ◽  
Organic Ligands ◽  
Keggin Type ◽  
Self Assembling ◽  
Behavioral Studies ◽  
Structures And Properties ◽  
Derivatives Of ◽  
Organic Fragment

Lacunary polyoxometalates (LPOMs) are key precursors for the synthesis of functional POMs. To date, reviews dedicated to behavioral studies of LPOMs often comprise the role of metal ions, including transition metal (TM) and rare earth (RE) ions, in extending and stability of high-nuclearity clusters. In contrast, the role of organic ligands in the structures and properties of lacunary-based hybrids has remained less explored. In this review, we focus on the role of organic fragments in the self-assembling process of POM-based architectures and discuss relationships between the nature and structure of organic ligand and properties such as the topology of hybrid inorganic–organic material in RE and TM-RE heterometallic derivatives of lacunary Keggin-type POMs. The effects of organic fragment in mixed ligand hybrids are also briefly reviewed.

Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2016 ◽  
Vol 12 (8) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

scholarly journals Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2013 ◽  
Vol 12 (5) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

Soluble carbohydrates in legume seeds

2012 ◽  
Vol 22 (4) ◽  
pp. 219-242 ◽  
Author(s):  
Ralph L. Obendorf ◽  
Ryszard J. Górecki
Keyword(s):  
Physiological Role ◽  
Dry Weight ◽  
Molecular Structures ◽  
Soluble Carbohydrates ◽  
Raffinose Family Oligosaccharides ◽  
Developing Seed ◽  
Legume Seeds ◽  
Galactosyl Cyclitols ◽  
Derivatives Of

AbstractMature dry legume seeds may contain up to 30 different soluble carbohydrates. Sucrose is a major component of the total soluble carbohydrates; others include the raffinose family oligosaccharides (RFOs; raffinose, stachyose, verbascose) that are mono-, di- and tri-α-galactosyl derivatives of sucrose. Other galactosides may include α-galactosyl derivatives of the cyclitols myo-inositol (galactinol, digalactosyl myo-inositol and trigalactosyl myo-inositol), d-pinitol (galactopinitol A, digalactosyl pinitol A (ciceritol) and trigalactosyl pinitol A; and galactopinitol B; higher galactosyl oligomers of galactopintiol B have rarely been detected), d-chiro-inositol (fagopyritol B1, fagopyritol B2 and fagopyritol B3) and d-ononitol (galactosyl d-ononitol and digalactosyl d-ononitol). Small amounts of myo-inositol, d-pinitol and d-chiro-inositol may also be present. Raffinose, stachyose and verbascose increase late in seed maturation, with 70% of RFOs accumulating after maximum seed dry weight is attained. RFOs are mostly degraded during germination. Sucrose, myo-inositol, d-pinitol and d-chiro-inositol are synthesized in maternal tissues of some legumes and are transported to and unloaded by seed coats into the apoplastic space surrounding developing seed embryos. Free cyclitols may be 60% of total soluble carbohydrates in leaves and 20% in seed coat cup exudates. Increasing the supply of free cyclitols may increase the accumulation of their respective α-galactosides in mature seeds. Seeds with reduced RFO accumulation, but with normal to elevated concentrations of galactosyl cyclitols (including fagopyritols), have normal field emergence and are also tolerant to imbibitional chilling under laboratory conditions. Molecular structures, biosynthetic pathways, accumulation of soluble carbohydrates in response to seed-expressed mutations and the physiological role of galactosides are reviewed.

scholarly journals Copper(I) π-complexes with allyl derivatives of heterocyclic compounds: structural survey of their crystal engineering

2013 ◽  
Vol 11 (12) ◽  
pp. 1875-1901 ◽  
Author(s):  
Yurii Slyvka ◽  
Evgeny Goreshnik ◽  
Oleksii Pavlyuk ◽  
Marian Mys’kiv
Keyword(s):  
Crystal Engineering ◽  
Heterocyclic Compounds ◽  
Organic Ligands ◽  
Π Complex ◽  
Complex Preparation ◽  
Preparation Route ◽  
Inorganic Constituents ◽  
Derivatives Of ◽  
Crystallochemical Analysis

AbstractIn this review an exhaustive crystallochemical analysis of copper(I) π-complexes with allyl derivatives of heterocyclic compounds has been performed. Structural genesis of inorganic constituents starting from the simplest units to the most complicated aggregates was considered taking into account the specific role of Cu-(C=C) interaction, the construction of the organic ligands, the basicity and nucleophilic activity of their heteroatoms, as well as olefin Cu(I) π-complex preparation route.

scholarly journals Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2008 ◽  
Vol 4 (1) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

Factors Affecting Molecular Self-Assembly and Its Mechanism

2012 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Hueyling Tan
Keyword(s):  
Self Assembly ◽  
Building Blocks ◽  
Molecular Engineering ◽  
Molecular Structures ◽  
Polymer Science ◽  
New Approach ◽  
Factors Affecting ◽  
Dna Structures ◽  
Self Assembling ◽  
Wide Range

Molecular self-assembly is ubiquitous in nature and has emerged as a new approach to produce new materials in chemistry, engineering, nanotechnology, polymer science and materials. Molecular self-assembly has been attracting increasing interest from the scientific community in recent years due to its importance in understanding biology and a variety of diseases at the molecular level. In the last few years, considerable advances have been made in the use ofpeptides as building blocks to produce biological materials for wide range of applications, including fabricating novel supra-molecular structures and scaffolding for tissue repair. The study ofbiological self-assembly systems represents a significant advancement in molecular engineering and is a rapidly growing scientific and engineering field that crosses the boundaries ofexisting disciplines. Many self-assembling systems are rangefrom bi- andtri-block copolymers to DNA structures as well as simple and complex proteins andpeptides. The ultimate goal is to harness molecular self-assembly such that design andcontrol ofbottom-up processes is achieved thereby enabling exploitation of structures developed at the meso- and macro-scopic scale for the purposes oflife and non-life science applications. Such aspirations can be achievedthrough understanding thefundamental principles behind the selforganisation and self-synthesis processes exhibited by biological systems.

The Role of Hydrophobicity in the Stability and pH-Switchability of (RXDX)4 and Coumarin-RXDX Conjugate β-Sheets

2020 ◽  
Author(s):  
Ryan Weber ◽  
Martin McCullagh
Keyword(s):  
Biological Imaging ◽  
Ph Sensing ◽  
Hydrophobic Residue ◽  
Ideal Candidate ◽  
Self Assembling ◽  
Sensing Applications ◽  
Β Sheets ◽  
The Stability ◽  
Dynamics Simulations

<p>pH-switchable, self-assembling materials are of interest in biological imaging and sensing applications. Here we propose that combining the pH-switchability of RXDX (X=Ala, Val, Leu, Ile, Phe) peptides and the optical properties of coumarin creates an ideal candidate for these materials. This suggestion is tested with a thorough set of all-atom molecular dynamics simulations. We first investigate the dependence of pH-switchabiliy on the identity of the hydrophobic residue, X, in the bare (RXDX)<sub>4</sub> systems. Increasing the hydrophobicity stabilizes the fiber which, in turn, reduces the pH-switchabilty of the system. This behavior is found to be somewhat transferable to systems in which a single hydrophobic residue is replaced with a coumarin containing amino acid. In this case, conjugates with X=Ala are found to be unstable and both pHs while conjugates with X=Val, Leu, Ile and Phe are found to form stable β-sheets at least at neutral pH. The (RFDF)<sub>4</sub>-coumarin conjugate is found to have the largest relative entropy value of 0.884 +/- 0.001 between neutral and acidic coumarin ordering distributions. Thus, we posit that coumarin-(RFDF)<sub>4</sub> containing peptide sequences are ideal candidates for pH-sensing bioelectronic materials.</p>

Exchange Spin Coupling from Gaussian Process Regression

2020 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Natnael Mogos ◽  
Jonny Proppe ◽  
Carmen Herrmann
Keyword(s):  
Machine Learning ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
Molecular Magnets ◽  
Molecular Structures ◽  
Spin Coupling ◽  
Structure Property ◽  
Data Set ◽  
Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

Directive Effect of Chain Length in Modulating Peptide Nano-assemblies

2020 ◽  
Vol 27 (9) ◽  
pp. 923-929
Author(s):  
Gaurav Pandey ◽  
Prem Prakash Das ◽  
Vibin Ramakrishnan
Keyword(s):  
Electron Microscopy ◽  
Amino Acids ◽  
Light Scattering ◽  
Chain Length ◽  
Self Assembly ◽  
The Self ◽  
Ionic Charge ◽  
Self Assembling ◽  
Biophysical Techniques

Background: RADA-4 (Ac-RADARADARADARADA-NH2) is the most extensively studied and marketed self-assembling peptide, forming hydrogel, used to create defined threedimensional microenvironments for cell culture applications. Objectives: In this work, we use various biophysical techniques to investigate the length dependency of RADA aggregation and assembly. Methods: We synthesized a series of RADA-N peptides, N ranging from 1 to 4, resulting in four peptides having 4, 8, 12, and 16 amino acids in their sequence. Through a combination of various biophysical methods including thioflavin T fluorescence assay, static right angle light scattering assay, Dynamic Light Scattering (DLS), electron microscopy, CD, and IR spectroscopy, we have examined the role of chain-length on the self-assembly of RADA peptide. Results: Our observations show that the aggregation of ionic, charge-complementary RADA motifcontaining peptides is length-dependent, with N less than 3 are not forming spontaneous selfassemblies. Conclusion: The six biophysical experiments discussed in this paper validate the significance of chain-length on the epitaxial growth of RADA peptide self-assembly.

The Role of microRNAs in the Viral Infections

2019 ◽  
Vol 24 (39) ◽  
pp. 4659-4667 ◽  
Author(s):  
Mona Fani ◽  
Milad Zandi ◽  
Majid Rezayi ◽  
Nastaran Khodadad ◽  
Hadis Langari ◽  
...  
Keyword(s):  
Viral Infections ◽  
Rna Viruses ◽  
Regulation Of Gene Expression ◽  
Molecular Structures ◽  
Main Function ◽  
Cellular Functions ◽  
Viral Genes ◽  
Non Coding Rnas ◽  
Post Transcriptional Regulation

MicroRNAs (miRNAs) are non-coding RNAs with 19 to 24 nucleotides which are evolutionally conserved. MicroRNAs play a regulatory role in many cellular functions such as immune mechanisms, apoptosis, and tumorigenesis. The main function of miRNAs is the post-transcriptional regulation of gene expression via mRNA degradation or inhibition of translation. In fact, many of them act as an oncogene or tumor suppressor. These molecular structures participate in many physiological and pathological processes of the cell. The virus can also produce them for developing its pathogenic processes. It was initially thought that viruses without nuclear replication cycle such as Poxviridae and RNA viruses can not code miRNA, but recently, it has been proven that RNA viruses can also produce miRNA. The aim of this articles is to describe viral miRNAs biogenesis and their effects on cellular and viral genes.

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