Nucleation kinetics,solubility, growth and characterization of novel semiorganic crystal—Bisthiourea zinc formate

Single crystals of bisthiourea zinc formate were grown by the low temperature solution growth technique. The nucleation parameters such as solubility, induction period, interfacial energy and metastable zone width, radius of critical nucleus, critical free energy barrier, number of molecules in the critical nucleus and energy per unit volume have been evaluated. Metastable and induction period values were determined experimentally in order to optimize the growth parameters. Transparent good quality single crystals are characterized by single crystal XRD, powder XRD and FTIR analysis. Optical and photoluminescence studies have been carried out for the grown crystal. The results have been discussed in detail.     

Growth and characterization of semi-organic nonlinear optical crystal

A new nonlinear optical crystal urea thiourea cadmium sulfate (UTCS) has been grown by slow evaporation technique in equimolar ratio. The grown crystals were characterized by single crystal X-ray diffraction analysis which reveals that sample crystallizes in triclinic system with non-centrosymmetric space group P1. The powder XRD pattern revealed the formation of UTCS compound. High-resolution-X-ray diffraction analysis was carried out to study the crystalline perfection of the sample. Functional groups of the grown crystal were identified by FT-IR studies. Thermo gravimetric and differential thermal analyses were employed to understand the thermal and physio-chemical stability of the synthesized compound. UV–Vis–NIR spectrum revealed the transmission properties of the crystal specimen. The SHG efficiency has been tested by the Kurtz powder technique using Nd: YAG laser and found to be about 0.82 times in comparison with standard KDP crystals.     

Autoacetylation of Purified Calreticulin Transacetylase Utilizing Acetoxycoumarin as the Acetyl Group Donor

Our earlier reports documented that calreticulin, a multifunctional Ca²⁺-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase (CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property of CRTAase by immunoblotting and mass spectrometry. Ca²⁺ was found to inhibit CRTAase activity. The inhibition of both autoacetylation of CRTAase as well as acetylation of the receptor protein was apparent when Ca²⁺ was included in the reaction mixture as visualized by interaction with anti-acetyl lysine antibody. The acetylation of lysines residues: −48, −62, −64, −153, and −159 in N-domain and −206, −207, −209, and −238 in P-domain of CRTAase were located by high-performance liquid chromatography-electronspray ionization tandem mass spectrometry. Further, computer assisted protein structure modeling studies were undertaken to probe the effect of autoacetylation of CRTAase. Accordingly, the predicted CRTAase 3D model showed that all the loop regions of both N- and P-domain bear the acetylated lysines. Energy minimization of the acetylated residues revealed charge neutralization of lysines due to the N-ε-acetylation which may facilitate the interaction of CRTAase with the protein substrate and the subsequent transacetylase action. An erratum to this article can be found at     

Calreticulin Transacetylase Mediates the Acetylation of Nitric Oxide Synthase by Polyphenolic Acetate

Our earlier investigations identified acetoxy drug: protein transacetylase (TAase), a unique enzyme in the endoplasmic reticulum (ER) catalyzing the transfer of acetyl groups from polyphenolic acetates (PA) to certain functional proteins. Recently we have established the identity of TAase with ER protein calreticulin (CR) and subsequently transacetylase function of CR was termed calreticulin transacetylase (CRTAase). CRTAase was purified and characterized from human placenta. CRTAase catalyzed the acetylation of a receptor protein nNOS, by a model PA 7, 8-diacetoxy-4-methylcoumarin (DAMC), which was visually confirmed by using antiacetyl lysine. The aim of this report was to provide tacit proof by providing mass spectrometry evidence for CRTAase catalyzed acetylation of purified nNOS by DAMC. For this purpose, purified nNOS was incubated with DAMC and CRTAase, the modified nNOS was analyzed by nanoscale LC-MS/MS, which recorded 11 distinct peptides with a significant score as acetylated on lysine residues. The distribution was in order: lysines-24, -33, -38, -131, and -229 of the PDZ domain, Lys-245 of the oxygenase domain, Lys-754 and -856 of FMN binding domain, Lys-989 of connecting domain and Lys-1300, -1321, and -1371 of the NADPH-binding domain were acetylated. The results documented in this paper highlighted for the first time modification of nNOS by way of acetylation. Our earlier work recorded the profound activation of platelet NADPH cytochrome P-450 reductase and the acetylation of the reductase protein by DAMC, which also remarkably enhanced intracellular levels of nitric oxide. The results reported here coupled with the aforementioned previous observations strongly implicate the possible role of the acetylation of the reductase domain of nitric oxide synthase (NOS) in the NOS activation. In addition, the acetylation of nNOS can be expected to potentiate the interaction with CR, eventually leading to the augmented catalytic activity of NOS and expression of the related biological effects.