Mode of interaction of calcium oxalate crystal with human phosphate cytidylyltransferase 1: a novel inhibitor purified from human renal stone matrix

Nephrolithiasis is a common clinical disorder, and calcium oxalate (CaOx) is the principal crystalline component in approximately 75% of all renal stones. It is widely believed that proteins act as inhibitors of crystal growth and aggregation. Acidic amino acids present in these proteins play a significant role in the inhibition process. In this study, interaction of cal-cium oxalate with human phosphate cytidylyltrans-ferase 1(CCT), a novel calcium oxalate crystal growth inhibitor purified from human renal stone matrix has been elucidated in silico and involvement of acidic amino acids in the same. As only sequence of CCT is available, henceforth its 3-D structure was modeled via Homology modeling using Prime module of Schrodinger package. Molecular dynamic simulation of modeled protein with solvation was done by mac-romodel (Schrodinger). The quality of modeled pro-tein was validated by JCSG protein structure valida-tion (PROCHECK & ERRAT) server. To analyze the interaction of modeled protein CCT with calcium oxalate along with role played by acidic amino acids, ‘Docking simulation’ was done using MOE–Dock. Interaction between calcium oxalate and CCT was also studied by substituting acidic amino acid in the active sites of the protein with neutral and positively charged amino acids. The in silico analysis showed the bond formation between the acidic amino acids and calcium atom, which was further substantiated when substitution of these acidic amino acids with alanine, glycine, lysine, arginine and histidine com-pletely diminished the interaction with calcium ox-alate.

Novel elastomeric spiropyran‑doped poly(dimethylsiloxane)optical waveguide for UV sensing

Novel poly(dimethylsiloxane)(PDMS)doped with two diferent spiropyran derivatives(SP)were investigated as potential candidates for the preparation of elastomeric waveguides with UV-dependent optical properties.First,free-standing flms were prepared and evaluated with respect to their photochromic response to UV irradiation.Kinetics,reversibility as well as photofatigue and refractive index of the SP-doped PDMS samples were assessed.Second,SP-doped PDMS waveguides were fabricated and tested as UV sensors by monitoring changes in the transmitted optical power of a visible laser(633 nm).UV sensing was successfully demonstrated by doping PDMS using one spiropyran derivative whose propagation loss was measured as 1.04 dB/cm at 633 nm,and sensitivity estimated at 115%change in transmitted optical power per unit change in UV dose.The decay and recovery time constants were measured at 42 and 107 s,respectively,with an average UV saturation dose of 0.4 J/cm2.The prepared waveguides exhibited a reversible and consistent response even under bending.The sensor parameters can be tailored by varying the waveguide length up to 21 cm,and are afected by white light and temperatures up to 70℃.This work is relevant to elastomeric optics,smart optical materials,and polymer optical waveguide sensors.