Identification and characterization of the novel nuclease activity of human phospholipid scramblase 1

Background

Human phospholipid scramblase 1 (hPLSCR1) was initially identified as a Ca²⁺ dependent phospholipid translocator involved in disrupting membrane asymmetry. Recent reports revealed that hPLSCR1 acts as a multifunctional signaling molecule rather than functioning as scramblase. hPLSCR1 is overexpressed in a variety of tumor cells and is known to interact with a number of protein molecules implying diverse functions.

Results

In this study, the nuclease activity of recombinant hPLSCR1 and its biochemical properties have been determined. Point mutations were generated to identify the critical region responsible for the nuclease activity. Recombinant hPLSCR1 exhibits Mg²⁺ dependent nuclease activity with an optimum pH and temperature of 8.5 and 37 °C respectively. Experiments with amino acid modifying reagents revealed that histidine, cysteine and arginine residues were crucial for its function. hPLSCR1 has five histidine residues and point mutations of histidine residues to alanine in hPLSCR1 resulted in 60 % loss in nuclease activity. Thus histidine residues could play a critical role in the nuclease activity of hPLSCR1.

Conclusions

This is the first report on the novel nuclease activity of the multi-functional hPLSCR1. hPLSCR1 shows a metal dependent nuclease activity which could play a role in key cellular processes that needs to be further investigated.

     

On the Distances between Latin Squares and the Smallest Defining Set Size

In this note, we show that for each Latin square L of order , there exists a Latin square of order n such that L and differ in at most cells. Equivalently, each Latin square of order n contains a Latin trade of size at most . We also show that the size of the smallest defining set in a Latin square is .     

Development and validation of a high-performance thin-layer chromatography method for the simultaneous quantification of rosmarinic acid,quercetin, glycyrrhizin and betulinic acid in polyherbal immunostimulant formulation

JPC – Journal of Planar Chromatography – Modern TLC - Quantification of bioactive markers through modern analytical methods is very essential for establishing the authenticity and...     

Thermally Stimulated Luminescence of Montmorillonite Clay

X-ray excited luminescence (XL) spectra of montmorillonite clay at RT showed a broad emission band around 380 nm with two shoulders at 340, 450 nm eitherside two sharp peaks and two shoulders are seen at 465, 487, and 548, 576 nm, respectively. The 548 and 576 nm peaks enhanced their intensity at LNT. Whereas thermally stimulated luminescence (TSL) revealed an intense glow peak at 355 K and a weak shoulder around 400 K. Room temperature annealing studies indicated that the 355 K glow peak is not as stable as 400 K shoulder which turns out to be a peak on RT annealing. The X-ray excited luminescence has been attributed to radiative recombination of electrons with holes which are associated with SiO^3-₄, AlO^4-₄ radicals and divalent impurities available in the naturally available clay. TSL is also understood on similar lines. Glow peak reactions are proposed tentatively and their trap parameters have been calculated.     

A hybrid approach for aeroacoustic analysis of the engine exhaust system

This paper presents a new hybrid approach for prediction of noise radiation from engine exhaust systems. It couples the time domain analysis of the engine and the frequency domain analysis of the muffler, and has the advantages of both. In this approach, cylinder/cavity is analyzed in the time domain to calculate the exhaust mass flux history at the exhaust valve by means of the method of characteristics, avoiding the tedious procedure of interpolation at every mesh point and solving a number of equations simultaneously at every junction. This is done by making use of an interrelationship between progressive wave variables of the linear acoustic theory and those of the method of characteristics. In this approach, nonlinear propagation in the exhaust pipe is neglected and free expansion is assumed at the radiation end of the exhaust pipe. In the case of a muffler proper, expansion from the exhaust pipe into the first chamber is assumed to be a free expansion. Various results of this approach are compared with those of the method of characteristics and the classical acoustic theory, and various peaks and troughs in insertion loss curves are analytically validated.     

4,4′-Bipyridyl complexes of iron: Magnetic,Mössbauer and other spectroscopic studies

Summary 4,4-Bipyridyl (4,4-bipy) complexes of ferrous salts of the Fe(4,4-bipy)_x(anion)_y type (where x or y=1 or 2) and of ferric salts of the Fe(4,4-bipy)_m(anion)_n type (where m=1 or 2 and n=3) have been synthesised. Elemental analyses, i.r. and electronic spectra, magnetic and Mössbauer studies have been performed to characterize the complexes. 4,4-Bipy and some anions are inferred to act as bridging ligands. The magnetic moments, electronic and Mössbauer spectra suggest that the complexes are of high spin type with distorted octahedral structures. The value of the isomer shift and quadrupole splitting are discussed in terms of bonding of the ligand and anions.     

Synthesis of phenazine derivatives for use as precursors to electrochemically generated bases

1,6-Disubstituted phenazine derivatives for use as precursors to electrochemically generated bases have been synthesized from readily available starting materials. Reaction of 1,6-dihydroxyphenazine with 1,10-diododecane, 1,11-diiodo-3,6,9-trioxaundecane or (R,R)-(-)-1,2-bis(3-iodopropoxy)cyclohexane gave planar chiral phenazinophanes containing ether-linked bridges; molecular structures of all these compounds have been determined by X-ray crystallography. Substituted 1,6-diaminophenazines were prepared by palladium-mediated amination of 1,6-dichlorophenazine and acylation of 1,6-diaminophenazine followed by reduction. Reaction of 1,6-bis(alkylamino)phenazines with sebacoyl chloride gave planar chiral phenazinophanes containing amide-linked bridges.     

Cobalt(II), nickel(II) and copper(II) complexes of bidentate bibenzimidazoles

Summary Complexes of cobalt(II), nickel(II) and copper(II) with novel bidentate bibenzimidazoles, [M(L-L)Cl₂], where L-L are methylenebis(1, 1-benzimidazole), methylenebis(2, 2-benzimidazole) and dimethylenebis(2, 2-benzimidazole) are described and characterized by different physical measurements. The four coordinate complexes have distorted tetrahedral or square coplanar structures. The bridging entity between the two donor groups apparently influences the ligand field strength and the ligands occupy a higher position than that of benzimidazole in the spectrochemical series.     

Reactivity ratios for the terpolymerization of methyl methacrylate,vinyl acetate,and molecular oxygen

The copolymerization of methyl methacrylate (MMA) and vinyl acetate (VAc) under high oxygen pressure was investigated. Copolyperoxides of various compositions were synthesized by the free‐radical‐initiated oxidative copolymerization of MMA and VAc monomers. The copolyperoxide compositions obtained from ¹H and ¹³C NMR spectra were used for determining the reactivity ratios of the monomers. The reactivity ratios indicated a larger proportion of MMA units statistically placed in the copolyperoxides. A theoretical analysis based on semiempirical AM1 calculations was performed to support the reactivity ratios. NMR studies showed irregularities in the copolyperoxide chain due to the cleavage reactions of the propagating peroxide radical. Thermal analyses of the copolyperoxides by differential scanning calorimetry gave evidence for the presence of alternating peroxide units in the copolyperoxide chain. The activation energies of thermal degradation suggested that degradation was controlled by the dissociation of the peroxide (? O? O? ) bond in the backbone of the copolyperoxide chain. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 564–572, 2002; DOI 10.1002/pola.10115     

Kinetics of formation of charge transfer complexes of poly(vinyl pyridines) with iodine, 7,7′8,8′-tetracyanoquinodimethane and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone by electronic spectroscopic studies

The kinetics of formation of charge transfer complexes of poly(4-vinyl pyridine), poly(2-vinyl pyridine), and poly(2-vinyl pyridine-co-styrene) with iodine, 7,7′,8,8′-tetracyanoquinodimethane and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone has been studied using electronic absorption spectroscopy. The charge transfer complexes of analogous low molecular weight donors, namely 2- and 4-picolines with the same set of acceptors have also been investigated for comparison. The composition and the equilibrium constants of the charge transfer complexes have been obtained. The equilibrium constant of the polymeric complexes is found to be higher than that of analogous complexes of the low molecular weight donors. A new method for determining the rate constants of the association and dissociation of the equilibrium involving the charge transfer complex formation has been proposed. The rate constants vary with the concentration of the acceptor. It indicates that the charge transfer complexes undergo a further reaction and hence the observed rate constants are not true but apparent rate constants. The charge transfer complexes have also been investigated by electron paramagnetic resonance spectroscopy.