Maruthi Konda

Lipase-catalyzed dissipative self-assembly of a thixotropic Peptide bolaamphiphile hydrogel for human umbilical cord stem-cell proliferation.

We report lipase-catalyzed inclusion of p-hydroxy benzylalcohol to peptide bolaamphiphiles. The lipase-catalyzed reactions of peptide bolaamphiphiles with p-hydroxy benzylalcohol generate dynamic combinatorial libraries (DCL) in aqueous medium that mimic the natural dissipative system. The peptide bolaamphiphile 1 (HO-WY-Suc-YW-OH) reacts with p-hydroxy benzylalcohol in the presence of lipase forming an activated diester building block. The activated diester building block self-assembles to produce nanofibrillar thixotropic hydrogel. The subsequent hydrolysis results in the dissipation of energy to form nonassembling bolaamphiphile 1 with collapsed nanofibers. The thixotropic DCL hydrogel matrix is used for 3D cell culture experiments for different periods of time, significantly supporting the cell survival and proliferation of human umbilical cord mesenchymal stem cells.

Controlling Peptide Self‐Assembly through a Native Chemical Ligation/Desulfurization Strategy

Self-assembled peptides were synthesized by using a native chemical ligation (NCL)/desulfurization strategy that maintained the chemical diversity of the self-assembled peptides. Herein, we employed oxo-ester-mediated NCL reactions to incorporate cysteine, a cysteine-based dipeptide, and a sterically hindered unnatural amino acid (penicillamine) into peptides. Self-assembly of the peptides resulted in the formation of self-supporting gels. Microscopy analysis indicated the formation of helical nanofibers, which were responsible for the formation of gel matrices. The self-assembly of the ligated peptides was governed by covalent and non-covalent interactions, as confirmed by FTIR, CD, fluorescence spectroscopy, and MS (ESI) analyses. Peptide disassembly was induced by desulfurization reactions with tris(2-carboxyethyl)phosphine (TCEP) and glutathione at 80 °C. Desulfurization reactions of the ligated peptides converted the Cys and penicillamine functionalities into Ala and Val moieties, respectively. The self-supporting gels showed significant shear-thinning and thixotropic properties.

Exploring thermodynamically downhill nanostructured peptide libraries: from structural to morphological insight

Here, we report the biocatalytic evolution of Nmoc (naphthalene-2-methoxycarbonyl)-capped dynamic combinatorial peptide libraries in the hydrogel state. Our approach is to use a biocatalyst, which can bring up the peptide self-assembly via synthesis and in situ self-organization of peptide oligomers under physiological conditions. The enzyme drives the amplification of Nmoc-capped peptide oligomers and leads to the generation of dynamic combinatorial libraries under physiological conditions via a reverse hydrolysis reaction. The enzyme permits reversible peptide synthesis as well as peptide hydrolysis reactions, which generate a preferred nanostructured component through peptide self-assembly. Nmoc-F/FF and Nmoc-L/LL systems have been used successfully to generate Nmoc-F3 and Nmoc-L5 as preferred components in the dynamic peptide libraries, which form helical nanostructures. The control experiment with a Nmoc-L/LLL system depicts the selection and preferred formation of a Nmoc-L5 library member via self-assembly. The library components are analysed by reverse phase high performance liquid chromatography (RP-HPLC) and mass spectrometry. The self-assembled nanomaterials are studied by rheology, fluorescence and time correlated single photon counting (TCSPC) spectroscopy. The secondary structure of the peptide components are analysed by FT-IR and circular dichroism (CD) spectroscopy. The self-assembled nanostructures are imaged by atomic force microscopy (AFM) and transmission electron microscopy (TEM).

Light induced construction of porous covalent organic polymeric networks for significant enhancement of CO2 gas sorption

Herein, we report morphology-controlled porous polymeric materials for enhanced CO2 capture, which was achieved using the topochemical polymerization of dipeptide functionalized diphenylbutadiynes. The topochemical reaction was executed to control the morphology of the synthesized dipeptide appended diarylbutadiyne derivatives on a solid surface. Topochemical polymerization involves the formation of polydiacetylene due to the presence of hydrogen bonding between the amide groups and intermolecular π–π stacking interactions in their self-assembled state, which was established using UV-Vis, Raman and IR spectroscopy. The change in morphology of the two dipeptide functionalized diphenylbutadiyne (DPB) was confirmed by scanning electron microscopy. Porosity was developed after UV irradiation of the diacetylene-based dipeptide appended bolaamphiphiles. Interestingly, after UV irradiation, the porous covalent organic polymers 1 and 2 show 24.22 times and 12 times enhanced N2 gas adsorption than their parent compounds 1 and 2, respectively. The surface area of the porous covalent organic polymers 1 and 2 was enhanced 21.68 times and 5.54 times than their parent compounds 1 and 2, respectively. Polymer 1 exhibits 4.23 times the CO2 capture ability than compound 1 and polymer 2 shows 4.1 times the CO2 capture ability than compound 2. This study highlights the controlled synthesis of light induced porous covalent organic polymers with high surface area used for efficient CO2 storage applications.

Redox-Active Peptide-Functionalized Quinquethiophene-Based Electrochromic π-Gel

An electrochromic system based on a self-assembled dipeptide-appended redox-active quinquethiophene π-gel is reported. The designed peptide-quinquethiophene consists of a symmetric bolaamphiphile that has two segments: a redox-active π-conjugated quinquethiophene core for electrochromism, and peptide motif for the involvement of molecular self-assembly. Investigations reveal that self-assembly and electrochromic properties of the π-gel are strongly dependent on the relative orientation of peptidic and quinquethiophene scaffolds in the self-assembly system. The colors of the π-gel film are very stable with fast and controlled switching speed at room temperature.