How are the ready and unready states of nickel-iron hydrogenase activated by H 2 ? A density functional theory studyw

We have explored possible mechanisms for the formation of the catalytically active Ni a -S state of the enzyme, nickel iron hydrogenase, from the Ni * r (ready) or Ni * u (unready) state, by reaction with H 2 , using density functional theory calculations with the BP86 functional in conjunction with a DZVP basis set. We find that for the reaction of the ready state, which is taken to have an -OH bridge, the rate determining step is the cleavage of H 2 at the Ni 3+ centre with a barrier of B15 kcal mol À1 . We take the unready state to have a -OOH bridge, and find that reaction with H 2 to form the Ni r -S state can proceed by two possible routes. One such path has a number of steps involving electron transfer, which is consistent with experiment, as is the calculated barrier of B19 kcal mol À1 . The alternative pathway, with a lower barrier, may not be rate determining. Overall, our predictions give barriers in line with experiment, and allow details of the mechanism to be explored which are inaccessible from experiment

Non-invasive Blood Glucose Quantification Using a Hybrid Sensor

Diabetes Mellitus is a group of metabolic diseases characterized by high blood sugar (glucose) levels which result from defects in insulin secretion. It is very important for the diabetics and normal people to have a correct blood glucose level. The HbA1c test is the most preferred test by renowned doctors for glucose quantification. But this test is an invasive one. At present, there are many available techniques for this purpose but these are mostly invasive or minimally non-invasive and most of these are under research. Among the different methods available, the photo acoustic (PA) methods provide a reliable solution since the acoustical energy loss is much less compared to the optical or other techniques. Here a novel framework is presented for blood glucose level measurement using a combination of the HbA1c test and a PA method to get an absolutely consistent and precise, non-invasive technique. The setup uses a pulsed laser diode with pulse duration of 5-15 ns and at a repetition rate of 10 Hz as the source. The detector setup is based on the piezoelectric detection. It consists of a ring detector that includes two double ring sensors that are attached to the ring shaped module that can be worn around the finger. The major aim is to detect the photo acoustic signals from the glycated hemoglobin with the least possible error. The proposed monitoring system is designed with extreme consideration to precision and compatibility with the other computing devices. The results obtained in this research have been studied and analyzed by comparing these with those of in-vitro techniques like the HPLC. The comparison has been plotted and it shows a least error. The results also show a positive drive for using this concept as a basis for future extension in quantifying the other blood components

How are the ready and unready states of nickel-iron hydrogenase activated by H2? A density functional theory study

This article compares verbal usage in two groups of Mexican children: one of third graders and the other of sixth graders. The empirical base is a sample of more than 3,800 compositions collected from primary schools all over the country. The verbs of each of the groups were obtained and categorized with respect to their meaning as perceptible and non-perceptible. More specifically, the verbs were sorted into reference sets including body and needs, psychological attributes, interpersonal relations, occupations and others. Based on these classifications, statistically significant semantic differences among younger and older children were established

Is corannulene a better diene or dienophile? A DFT analysis

Diels Alder reactivity of corannulene has been probed using density functional theory (DFT) at B3LYP/6-31G level by employing it both as a diene and a dienophile in cycloaddition with ethylene and 1,3-butadiene as typical partners. Computations reveal that corannulene acts better as a dienophile than as a diene and as a dienophile it undergoes normal electron demand type addition with 1,3-butadiene, and as a diene corannulene undergoes inverse electron demand type addition with ethylene. When employed as a dienophile the addition takes place preferentially in the rim position than in the spoke position due to strong steric and electronic reasons. Further in the rim addition rim exo approach is favored kinetically and thermodynamically. As a diene, corannulene shows regioselectivity for rim-spoke addition over spoke-spoke addition. Concerted type cycloadditions have been studied and the reactions are seen to take place preferentially on the convex face. The effect of substituents in butadiene on the reactivity and the reaction of butadiene-pentaindenocorannulene (an extended corannulene) system has been investigated for the most favorable rim exo positions