Thiamin pyrimidine biosynthesis in Candida albicans : a remarkable reaction between histidine and pyridoxal phosphate

In Saccharomyces cerevisiae , thiamin pyrimidine is formed from histidine and pyridoxal phosphate (PLP). The origin of all of the pyrimidine atoms has been previously determined using labeling studies and suggests that the pyrimidine is formed using remarkable chemistry that is without chemical or biochemical precedent. Here we report the overexpression of the closely related Candida albicans pyrimidine synthase (THI5p) and the reconstitution and preliminary characterization of the enzymatic activity. A structure of the C. albicans THI5p shows PLP bound at the active site via an imine with Lys62 and His66 in close proximity to the PLP. Our data suggest that His66 of the THI5 protein is the histidine source for pyrimidine formation and that the pyrimidine synthase is a single-turnover enzyme.     

Effect of Gold Nanosphere Surface Chemistry on Protein Adsorption and Cell Uptake In Vitro

Gold nanoparticles exhibit unique spectral properties that make them ideal for biosensing, imaging, drug delivery, and other therapeutic applications. Interaction of gold nanoparticles within biological environments is dependent on surface characteristics, which may rely on particular capping agents. In this study, gold nanospheres (GNS) synthesized with different capping agents??specifically citric acid (CA) and tannic acid (TA)??were compared for serum protein adsorption and cellular uptake into a lung epithelial cell line (A549). Both GNS samples exhibited noticeable protein adsorption based on surface charge data after exposure to serum proteins. Light scattering measurements revealed that GNS-CA-protein composites were smaller and less dense compared to GNS-TA-protein composites. The cell uptake characteristics of these nanoparticles were also different. GNS-CA formed large clusters and elicited high uptake, while GNS-TA were taken up as discrete particles, possibly through nonendosomal mechanisms. These results indicate that the capping agents used for GNS synthesis result in unique biological interactions.     

Zn(II) based colorimetric sensor for ATP and its use as a viable staining agent in pure aqueous media of pH 7.2

Selective colorimetric detection of ATP in physiological conditions by a Zn(II)-based receptor is reported. This reagent was found to be non-toxic to the living cells and could be used for studying the growth of the yeast cells.     

Electrical and electrochemical studies on magnesium ion-based polymer gel electrolytes

The development of polymer gel electrolyte system with high ionic conductivity is the main objective of polymer research. Electrochemical devices based on lithium ion-conducting polymer electrolyte are not safe due to the explosive nature of lithium. An attempt has been made to synthesize magnesium ion-conducting polymeric gel electrolytes, poly (vinylidene fluoride-co-hexafluoropropylene)–propylene carbonate–magnesium perchlorate, PVdF(HFP)-PC–Mg(ClO₄)₂ using standard solution-cast techniques. The maximum room temperature ionic conductivity of the synthesized electrolyte system has been observed to be 5.0 × 10⁻³ S cm⁻¹, which is quite acceptable from a device fabrication point of view. The temperature-dependent conductivity and the dielectric behavior were also analyzed. The pattern of the temperature-dependent conductivity shows the Arrhenius behavior. The dielectric constant ε _r and dielectric loss ε _i increases with temperature in the low-frequency region but almost negligible in the high-frequency region. This behavior can be explained on the basis of electrode polarization effects. The real part M _r and imaginary part M _i versus frequency indicate that the systems are predominantly ionic conductors. Further, the synthesized electrolyte materials have been checked for its suitability in energy storage devices namely redox supercapacitor with conducting polymer polypyrrole as electrode materials, and finally, it was observed that it shows good capacitive behavior in low-frequency region. Preliminary studies show that the overall capacitance of 22 mF cm⁻² which is equivalent to a single electrode specific capacitance of 117 F gm⁻¹ was observed for the above said supercapacitors.     

Evaluation of DNA Binding with Some Selected Hydrazide and Semicarbazide Derivatives

A group of hydrazide and semicarbazide derivatives containing isopropylidene, benzylidene, cyclohexylidene, and phospholidene groups was synthesized and characterized by spectroscopic techniques. These compounds were tested for DNA interaction studies monitored by UV-Vis and IR data as well as molecular docking. Investigations on interactions of these compounds with DNA revealed an intercalative mode of binding between them. It is interesting to note that semicarbazide derivatives with aliphatic substituents showed better DNA binding than the aromatic substituents.     

Ligand‐based design,virtual screening,and ADME/T‐based profiling on a dataset of 1,3,5‐triazine‐substituted benzene sulfonamides as carbonic anhydrase inhibitors

A quantitative structure–activity relationship (QSAR) analysis was performed on a dataset of 62 (1,3,5‐triazine‐substituted) benzene sulfonamides as carbonic anhydrase II and IX inhibitors using simulated annealing‐based multiple linear regression analysis. The selected QSAR model for carbonic anhydrase II inhibition (cross‐validated Q² = 0.689, , ) showed that aromaticity, lipophilicity, electronegativity, and molecular projection in the XZ plane influence the activity, whereas that for carbonic anhydrase IX inhibition (cross‐validated Q² = 0.767, , ) showed that activity was influenced by hydrophilicity, linker between the aromatic rings, electronegativity, and molecular weight. The QSAR model selected was internally and externally validated to define its predictability. Activity prediction of an external dataset containing nine compounds (within the same sphere of applicability) was performed to prove the models' specificity, selectivity, and sensitivity. The hypothesis in the form of the QSAR model was used for ligand‐based virtual screening on the ZINC database to obtain some potential hits. Similarly, docking studies on screened hits showed that the molecules interact and orient at the catalytic site in a way similar to acetazolamide. Additionally, an absorption, distribution, metabolism, excretion, and toxicity screening was also performed, and results showed that most of the compounds that can be possible drug candidates obey the Lipinski rule of five and Jorgensen rule of three. Copyright © 2013 John Wiley & Sons, Ltd.     

Syntheses and Characterization of New Vinyl‐Borylene Complexes by the Hydroboration of Alkynes with [(μ3‐BH)(Cp*RuCO)2(μ‐CO)Fe(CO)3]

Room temperature photolysis of a triply‐bridged borylene complex, [(μ₃‐BH)(Cp*RuCO)₂(μ‐CO)Fe(CO)₃] ( 1 a ; Cp*=C₅Me₅), in the presence of a series of alkynes, 1,2‐diphenylethyne, 1‐phenyl‐1‐propyne, and 2‐butyne led to the isolation of unprecedented vinyl‐borylene complexes (Z)‐[(Cp*RuCO)₂(μ‐CO)B(CR)(CHR′)] ( 2 : R, R′=Ph; 3 : R=Me, R′=Ph; 4 : R, R′=Me). This reaction permits a hydroboration of alkyne through an anti ‐ Markovnikov addition. In stark contrast, in the presence of phenylacetylene, a metallacarborane, closo‐[1,2‐(Cp*Ru)₂(μ‐CO)₂{Fe₂(CO)₅}‐4‐Ph‐4,5‐C₂BH₂] ( 5 a) , is formed. A plausible mechanism has been proposed for the formation of vinyl‐borylene complexes, which is supported by density functional theory (DFT) methods. Furthermore, the calculated ¹¹B NMR chemical shifts accurately reflect the experimentally measured shifts. All the new compounds have been characterized in solution by mass spectrometry and IR, ¹H, ¹¹B, and ¹³C NMR spectroscopies and the structural types were unequivocally established by crystallographic analysis of 2 , 5 a , and 5 b .     

The synthesis of aza-β-lactams via tandem Petasis-Ugi multi-component condensation and 1,3-diisopropylcarbodiimide (DIC) condensation reaction

The synthetic utility of a tandem Petasis-Ugi multi-component condensation and 1,3-diisopropylcarbodiimide condensation reactions have been employed to efficiently prepare two to four-dimensional libraries of aza-β-lactams.