DFT, ab initio, NMR, and NBO analyses of N-substituted hydrazino acetamides: Experimental vs theoretical values

We studied the DFT (B3LYP) and HF at 6-31+G/6-31+G^∗∗ levels of theory in order to throw light on the conformation, structure, intramolecular hydrogen bond network, as well as proton and nitrogen NMR (GIAO method) of a series of model primary amides in the gas phase and/or in solution (chloroform, methanol, water, dimethyl sulfoxide, and heptane). In this manner, it was possible to show that the amidic group of these model compounds acts as the H-bond donor and interacts with two different H-bond acceptors, thus stabilizing the C₈ pseudocycle. The study was conducted to gain a better understanding of the conformation (both experimentally and theoretically) adopted by hydrazino acetamides (model compounds for aza-β³-peptides). In the light of this, we were able to explain why aza-β³-peptides develop a different H-bond network in comparison to their isosteric β³-peptide analogues (an extension of the β-peptide concept).     

Mechanisms of antioxidant action: The role of copper salts in the photostabilization of paint media

Verdigris, a copper pigment containing basic copper acetate hydrate, is an effective light stabilizer for linseed oil based paint media but gives rise to discolouration over a long period. The antioxidant process is shown to result in the formation of conjugated chromophores in the medium. A catalytic antioxidant mechanism involving redox reactions of the copper ions is proposed to account for the efficiency of the pigment as a light stabilizer.     

A combined structure-based pharmacophore modeling and 3D-QSAR study on a series of N-heterocyclic scaffolds to screen novel antagonists as human DHFR inhibitors

Structural Chemistry - Dihydrofolate reductase (DHFR) is an essential enzyme that participates in folate metabolism and purine and thymidylate synthesis in cell proliferation. It converts...     

New insights into the selective inhibition of the β-carbonic anhydrases of pathogenic bacteria Burkholderia pseudomallei and Francisella tularensis: a proteochemometrics study

Molecular Diversity - Nowadays, antibiotic resistance has turned into one of the most important worldwide health problems. Biological end point of critical enzymes induced by potent inhibitors is...     

Effects of imperfect products on lot sizing with work in process inventory

The economic production quantity (EPQ) is one of the most widely known inventory control models that can be regarded as the generalized form of the Economic Order Quantity. However, the model is built on an unrealistic assumption that all the produced items need to be of perfect quality. Also, the introduction of work in process, WIP, as part of the inventory has been of lesser concern in developing inventory models. This paper attempts to develop the economic production quantity considering work in process inventory and manufacturing imperfect products that may be either reworkable or non-reworkable. The non-reworkable imperfect products are sold at a reduced price. This paper introduces a new model for this problem.     

Structure Function of the Bound Proton in the Dressed-quark Exchange Formalism

The idea of the dressed quark scenario, in the context of the quark exchange model has been used to obtain the bound parton distribution functions as well as the bound proton structure function. The Glück, Reya, and Vogt (GRV)’s parton distribution functions, where they have a good agreement with the experimental data in the whole range of (x, Q²)-region, have been used to extract the amount of the momentum carried by each parton inside the proton; therefore, by using these values, the different parton densities inside the constituent quark have been calculated. To extract the parton distribution functions in the bound proton, the phenomenological constituent quark exchange formalism and the nuclear convolution theorem have been used. By considering these densities, the structure function of the bound proton, \({F_{2}^{P}}(x,Q^{2})\), inside the light nuclei like helium-3 or tritium has been calculated at low- and high-Q² values. The correctness of the calculations has been tested through computing the difference of the proton-neutron structure functions as well as the ratio of the neutron to the proton structure functions, in which they are well known from experimental data. The results of the present study are in an agreement with both the available and relevant experimental data and the theoretical predictions.

     

DFT and ab initio potential energy scan and hydrogen bond analysis of N-substituted hydrazino acetamides: Characterization of the “hydrazinoturn” hydrogen bonding pattern

We studied a series of model primary amides in gas phase at the DFT (B3LYP) and HF at 6-31+G/6-31+G** levels of theory in order to shed light on their conformation, structure, and intramolecular hydrogen bonding network. A potential energy scan was performed by rotating around the appropriate bond for each molecule studied in this paper. In this manner, it was possible to show that the amidic group of these model compounds acts as H-bond donor and interacts with two different H-bond acceptors which stabilizes a C₈ pseudocycle, the so called “hydrazinoturn”. This study was addressed theoretically in order to understand the conformation adopted by hydrazino acetamides as model compounds for aza-β³-peptides. We thus investigated the conformational analysis of hydrazinoturns computationally and showed that these systems represent a very stabilizing folding driving force, provided that the neighboring molecular functional groups do not imply other competing hydrogen bonding patterns.     

The Constituent Quark Exchange Model for the Bound State Nucleons

The aim of present article is to compare the different bound state parton distributions in the protons with those coming from the free protons experimental data and to investigate the effect of quark structure of protons on each other. So, the constituent quark model (CQM), in which the quarks are assumed to be the complex objects and was originally proposed by Altarelli et al. (ACMP), is used in the frame work of the quark exchange model (QEM) to calculate the parton distributions of bound protons. Unlike our previous works, the effect of sea quarks and gluons are included in the QEM. Our results are in agreement with those of Glück et al. (GRV) when we ignore the binding and the Fermi motion effects for the constituent quarks. In this case, we get more sea-quarks and gluons with respect to the bound state constituents quarks calculation. It is also shown that the QEM, which is a realistic formalism gives better result with respect to the Isgur and Karl et al. model which is a field theoretical approach. The ratio of the structure functions of neutron to proton is also calculated with the assumption of isospin symmetry and it is compared with the available data and our previous works.     

The Structure Functions of 3 He and 3 H Nuclei in the Constituent Quark Exchange Model

The valence quark exchange (QE) model for the nuclear system and the constituent quark (CQ) model in which the quarks are assumed to be the complex objects, are used to calculate the parton distributions and the structure functions (SF) of ³ He and ³ H mirror nuclei. The effect and the role of sea quarks and gluons, and their contributions to the SF of ³ He and ³ H nuclei are analyzed. Specifically, for small x regions a more “realistic” result is found with respect to our previous works, in which only the valence quarks have been considered. By using the DGLAP evolution equations, the resulting parton distributions and SF are evolved to the high-energy scales and compared with available data. Finally, the ratios of ³ He to ³ H nuclei SF with the isospin symmetry assumption is compared to the results of the deep inelastic electron experiments on the ³ He and ³ H nuclei, especially, those which have been extracted from the kinematic region of the proposed 11 GeV upgraded beam experiment of Jefferson laboratory, and a reasonable agreement is found.     

A flexible microfluidic processor for molecular biology: application to microarray sample preparation

We describe a programmable microfluidic system with onboard pumps and valves that has the ability to process reaction volumes in the sub-microlitre to hundred microlitre range. The flexibility of the architecture is demonstrated with a commercial molecular biology protocol for mRNA amplification, implemented without significant modification. The performance of the microchip system is compared to conventional bench processing at each stage of the multistep protocol, and DNA microarrays are used to assess the quality and performance of bench- and microchip-amplified RNA. The results show that the microchip system reactions are similar to bench control reactions at each step, and that the microchip- and bench-derived amplified RNAs are virtually indistinguishable in differential microarray analyses.