Browsing by Author "Sadhu, K.K."

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    Diverse interactions of aggregated insulin with selected coumarin dyes: Time dependent fluorogenicity, simulation studies and comparison with thioflavin T
    (Elsevier Ltd, 2021) Dalal, S.; Das, B.K.; Saini, M.; Chakraborty, D.; Sadhu, K.K.
    In this study, we have compared neutral coumarin based well-known commercially available probes C6, C7 and C545T for fluorogenic response from the aggregated insulin. The immediate fluorogenic responses were comparatively poor from all the three probes with respect to the previously reported response from thioflavin T (ThT) in the presence of aggregated insulin. Interestingly C6 among the three neutral coumarin derivative showed a significant steady increase of fluorescence intensity with time up to 6 h before reaching the saturation limit. Similar time dependent fluorogenic experiment with C7, C545T and ThT showed comparatively fast saturation within few minutes to 2 h. The molecular docking and simulation studies showed that these neutral probes could be stabilized in the aggregated form of the insulin predominantly by non-covalent weak interactions such as hydrogen bonding, ?-? and cation-? interactions. The probability distributions of the dihedral angles between two heterocyclic parts in C6 showed maximum probability of occurrence at 0° and 180°. These probability distributions of the dihedral angles between two heterocyclic parts within all the four fluorophores provided the justification of selective time dependent fluorescence enhancement from C6 in presence of insulin aggregate. The overall fluorogenic enhancement from C6 was comparable to the fluorogenic response from ThT and theoretical study confirmed distinctly different origin of this associated slow time dependent fluorogenic response. © 2020 Elsevier Ltd
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    Growth Reaction of Gold Nanorods in the Presence of Mutated Peptides and Amine-Modified Single-Stranded Nucleic Acids
    (John Wiley and Sons Ltd, 2023) Sahu, J.K.; Singh, O.; Chakraborty, D.; Sadhu, K.K.
    Conformation of biomolecules like DNA, peptides and amino acids play vital role during nanoparticle growth. Herein, we have experimentally explored the effect of different noncovalent interaction between a 5′-amine modified DNA sequence (NH2−C6H12-5′-ACATCAGT-3′, PMR) and arginine during the seed-mediated growth reaction of gold nanorods (GNRs). Amino acid-mediated growth reaction of GNRs results in a snowflake-like gold nanoarchitecture. However, in case of Arg, prior incubation of GNRs with PMR selectively produces sea urchin-like gold suprastructures, via strong hydrogen bonding and cation-π interaction between PMR and Arg. This distinctive structure formation strategy has been extended to study the structural modulation caused by two structurally close α-helical RRR (Ac-(AAAAR)3A−NH2) peptide and the lysine mutated KKR (Ac−AAAAKAAAAKAAAARA−NH2) peptide with partial helix at the amino terminus. Simulation studies confirm that a greater number of hydrogen bonding and cation-π interaction between the Arg residues and PMR resulted in the gold sea urchin structure for RRR peptide against KKR peptide. © 2023 Wiley-VCH GmbH.