Reduced fluorescence quenching of coumarin 102 at higher phenol mole fractions in cyclohexane–phenol and anisole–phenol solvent mixtures: role of competitive hydrogen bonding

RSC Advances ◽  
2014 ◽  
Vol 4 (102) ◽  
pp. 58299-58306 ◽  
Author(s):  
Nabajeet Barman ◽  
Kalyanasis Sahu
Keyword(s):  
Hydrogen Bonding ◽  
Fluorescence Quenching ◽  
Solvent Mixtures ◽  
Coumarin 102

Role of solvent polarity on fluorescence quenching of 3MOCE in binary solvent mixtures

2020 ◽  
Author(s):  
S. Vaijayanthimala ◽  
Kalpana Sharma ◽  
Raveendra Melavanki ◽  
P. Bhavya ◽  
U. Meghana ◽  
...  
Keyword(s):  
Fluorescence Quenching ◽  
Solvent Polarity ◽  
Binary Solvent ◽  
Solvent Mixtures ◽  
Binary Solvent Mixtures ◽  
Role Of Solvent

scholarly journals The role of nitro groups in the binding of nitroaromatics to protein MOPC 315

1978 ◽  
Vol 173 (3) ◽  
pp. 713-722 ◽  
Author(s):  
P Gettins ◽  
D Givol ◽  
R A Dwek
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
High Resolution ◽  
Hydrogen Bonds ◽  
Fluorescence Quenching ◽  
Nitro Group ◽  
Protein Interactions ◽  
Chemical Shifts ◽  
Binding Constants

Two series of dinitrophenyl haptens, in which chlorine replaces one or both nitro groups, were used to investigate, by a combination of high-resolution 1H n.m.r. and fluorescence quenching, the presence of groups in the combining site of protein MOPC 315, which form hydrogen bonds to the aromatic-ring substituents of the hapten. The large differences in binding constants on successive replacement of nitro groups were shown to be due to specific hapten-substituent-protein interactions by (a) showing that there was little difference in the interaction between these haptens and 3-methylindole (a model for the residue tryptophan-93L with which the hapten stacks in protein MOPC 315), (b) proving by 1H n.m.r. that the mode of hapten binding is constant and (c) showing that the differences in Kd were consistent with the relative hydrogen-bonding capacities of chlorine and the nitro moiety. In this way it was established that each nitro group forms a hydrogen bond. Furthermore, from consideration of the 1H n.m.r. chemical shifts of several dinitrophenyl haptens and their trinitrophenyl analogues, it was shown that there is no distortion of the o-nitro group on binding to the variable fragment of protein MOPC 315.

Preferential solvation of p-nitroaniline in a binary mixture of chloroform and hydrogen bond acceptor solvents: the role of specific solute–solvent hydrogen bonding

2020 ◽  
Vol 22 (6) ◽  
pp. 3545-3562 ◽  
Author(s):  
Prakash Kumar Malik ◽  
Madhusmita Tripathy ◽  
Aravind Babu Kajjam ◽  
Sabita Patel
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Binary Mixture ◽  
Preferential Solvation ◽  
Binary Solvent ◽  
Local Concentration ◽  
Solvent Mixtures ◽  
Hydrogen Bond Acceptor ◽  
Binary Solvent Mixtures

Solute–solvent H-bonding in binary solvent mixtures may increase the local concentration at specific sites resulting in location specific preferential solvation.

scholarly journals Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2074
Author(s):  
Sara Tabandeh ◽  
Cristina Elisabeth Lemus ◽  
Lorraine Leon
Keyword(s):  
Hydrogen Bonding ◽  
Phase Separation ◽  
Liquid Phase ◽  
Charge Density ◽  
Secondary Structures ◽  
Liquid Phase Separation ◽  
Polyelectrolyte Complexes ◽  
Π Interactions ◽  
Liquid Liquid Phase Separation

Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

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