• DEBAPRATIM DAS

Articles written in Bulletin of Materials Science

• pH and secondary structure instructed aggregation to a thixotropic hydrogel by a peptide amphiphile

Peptide-amphiphile (PA)-based supramolecular thixotropic hydrogels are useful in medical sciences due to multiple advantageous features along with its biocompatibility and biodegradability. In this work, we have developed aself-assembled peptide-based hydrogel from a $\beta$-sheet forming short PA. Hydrogelation of the PA is controlled by pH and consequent changes in secondary structures attained by the PA. Under acidic conditions, the PA remains in random coil conformation. While increasing the pH to 9, a rapid transformation to anti-parallel β-sheet leads to a strong hydrogel. Interestingly, the disulphide-linked dimer of the PA failed to attain such aggregation pattern. The pH-induced sol–gel–sol transition can be achieved for several cycles without any change in aggregation pattern. The hydrogel was also found to show thixotropic rheological behaviour and thus, it can be utilized as an injectable hydrogel for biomedical applications.

• Molecular dynamics simulations of a stacked $\pi$-conjugated soft material: binding energy and preferential geometry for self-assembly

Understanding intermolecular interactions among supramolecular self-assembled organization and identifying the molecular structure relevant to the self-assembly are crucial for designing materials with desired functionalities. Interactions of aromatic rings in a peptide–perylenediimide conjugate (P-1) are investigated using dispersion-corrected density functional theory. The binding energies of fully optimized dimeric P-1 are calculated to identify the most stable conformation of the dimer. We show that the dispersion correction terms have significant contributions to the total energies of the dimers. The combined results from electronic structure calculations and molecular dynamics simulations demonstrate that the stacked dimer with negative inter-planar angle with clock-wise rotation has stronger binding energy than the dimer with positive inter-planar angle. The excess stability of the dimer with clock-wise rotation is attributed to the intra- and inter-molecular π–π stacking of the side aromatic rings of the dimer facilitated by formation of less number of hydrogenbonds. The stacked P-1 dimer with negative inter-planar angle and stronger binding energy is identified as the building block of a super structure with left-handed helical arrangements. Our calculations will build the first step towards understanding the molecular origin of the stability of a specific super structure of P-1 over the other, as obtained in the experiment relevant to material science and technology.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020