Journal of Sciences, Islamic Republic of Iran
Volume:24 Issue: 1, Winter 2013

Pyruvate kinase is a key enzyme in glycolytic pathway that catalyzes the transphosphorylation between phosphoenolpyruvate and ADP to yield ATP and Pyruvate. Geobacillus stearothermophillus has a stable pyruvate kinase with determined crystal structure that composed of four separate domains. Given that limited proteolysis experiments can be successfully used to probe conformational features of proteins, in this study we obtained useful information on Geobacillus pyruvate kinase using limited proteolysis with two proteases that have different substrate specificity and optimum temperature of activity, trypsin and thermolysin. Proteolytic patterns at different temperatures indicate that resulting fragments were the same but the rate of digestion increased with temperature. In the next step, Sucrose and Glycine were used to examine the effects of additives on stability and activity of pyruvate kinase. Limited proteolysis was carried out at 37 °C by trypsin and at 30, 55 and 60 °C in presence of thermolysin, in the absence and presence of different concentrations of sucrose (0– 1.5 M) and glycine (0–1.5 M). We observed that stabilization of pyruvate kinase by this osmolytes is concentration dependent and the rate of limited proteolysis in presence of additives, at temperatures above 60 °C decrease; however, there was no any effect on proteolytic patterns. In all experiments the activity of pyruvate kinase was determined with a couple assay methods by luciferase. A clear correlation was observed between proteolytic digestion and enzyme activity. This study reveals a number of flexible and protease-prone regions of pyruvate kinase that exist regardless of the environmental conditions.

The combinations of inductively coupled plasma-optical emission spectrometry (ICP-OES) and three classification algorithms, i.e., partial least squares discriminant analysis (PLS-DA), least squares support vector machine (LS-SVM) and soft independent modeling of class analogies (SIMCA), for discriminating different brands of Iranian bottled mineral waters, were explored. ICP-OES was used for the determination of Li, Na, K, Ca, Mg, Sr, Ba, B, Si and Zn in bottled mineral waters (150 samples) from 30 brands. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) showed differences in water samples according to the mineral composition. 120 samples (4 for each brand) were selected randomly for the calibration set, and 30 samples (1 for each brand) for the prediction set. PLS-DA, LS-SVM and SIMCA were implemented for calibration models. The results suggest that ICP-OES combined with PLS-DA, LS-SVM and SIMCA models had the capability to discriminate the different brands of mineral waters with high accuracy. The model can resolve the tap water samples from classified mineral waters accordingly.

Baft ophiolite mélange is a part of Naein-Baft ophiolite (southeast of Kerman province in Iran). Serpentinites from Baft ophiolite mélange contain different types of spinels such as chromite, chromespinel, ferritchromite and magnetite which can reveal different stages of evolution in host serpentinites. The compositions of Baft chromites show that they belong to podiform chromitites that may have crystallized from boninitic magmas. It seems that the Baft chromitite ores initially have been formed in a primary ophiolitic complex within dunitic envelopes; In the next stage, due to serpentinization of the peridotites and ascending of the resulted serpentinite, the studied deposits have been emplaced along the shear zones of the Baft ophiolitic melange. The compositions of primary Cr-spinels show that the Baft ophiolite has been formed in a suprasubduction zone in an arc/back-arc environment and the host rocks represent serpentinized Alpine type mantle residual peridotites. These studies suggest that the first serpentinization has taken place in an ocean floor environment and in this stage, mesh-textured serpentinites formed under static conditions. Then, the main serpentinization occurs and Cr-spinels have progressively replaced by ferritchromite rims, probably due to regional metamorphism. It seems that in the studied area, flare-textured serpentinites have passed higher temperature and pressure, and their formation can be related to dynamic evolutions such as subduction of Naein-Baft oceanic slab beneath the central Iranian microcontinent. Probably, the formation of magnetite fibers (type II) have accompanied by deformation process, while idiomorphic magnetites (type I) have produced from the passing Fe-rich fluids.

Kuh-E-Faryadoon and Kouli Kosh iron deposits are hosted by regional metamorphic rocks of Sanandaj-Sirjan zone around Deh-Bid area. Plugs and domes of acid rocks protrude these metamorphic rocks. A mylonitization event is super imposed on acid rock and metamorphic complexes. Field, petrological and geochemical studies have shown that (1) Iron mineralization have occurred during mylonitization in N45W shear zones. (2) Mineralization have many characteric pecularities of IOCG hydrothermal deposits. (3) Mylonitization is super imposed on regional metamorphism therefore early paragenesis of regional metamorphism are destabilized and new paragenesis are formed. (4) Iron is released through destabilization of biotite, clinopyroxene, epidote, ilmenite and titanomagnetite of mafic metamorphic rock (mainly greenschists) and acid rocks during mylonitization event. Petrographic evidences and relevant reaction are presented and discussed. (5) Iron is mainly and preferentially released from greenschists. (6) Transport of iron by carbonile complexes are proposed based on direct evidence of Co2 rich solutions during mylonitization.

In this paper, we prove the strong uniform consistency and asymptotic normality of the kernel density estimator proposed by Jones [12] for length-biased data.The approach is based on the invariance principle for the empirical processes proved by Horváth [10]. All simulations are drawn for different cases to demonstrate both, consistency and asymptotic normality and the method is illustrated by real automobile brake pads data.

This paper deals with continuous frames and continuous Riesz bases. We introduce continuous Riesz bases and give some equivalent conditions for a continuous frame to be a continuous Riesz basis. It is certainly possible for a continuous frame to have only one dual. Such a continuous frame is called a Riesz-type frame [13]. We show that a continuous frame is Riesz-type if and only if it is a continuous Riesz basis. Finally we find a measure with respect to which, a continuous wavelet frame is a continuous Riesz basis.

In this paper, we apply the differential transform (DT) method for finding approximate solution of the system of linear and nonlinear Volterra integro-differential equations with variable coefficients, especially of higher order. We also obtain an error bound for the approximate solution. Since, in this method the coefficients of Taylor series expansion of solution is obtained by a recurrence relation, thus we can use arbitrary number of Taylor series terms to obtain solutions with desired accuracy. Here we give some preliminary results of the differential transform and show that the DT method can be easily applied to a wide class of linear and nonlinear systems. Finally, the accuracy and simplicity of this method will be verified by solving some examples.

We calculate the stopping power for heavy-ion diclusters moving in a strongly coupled two-dimensional electron gas system by using the local field corrected dielectric function at finite temperature. We obtain a parameterized local field correction factor based on a relation between the thermal compressibility and exchange-correlation energy in two-dimension. The interpolated parameter is derived from the Monte-Carlo data for the exchange-correlation energy of a two-dimensional electron gas system. We compare our results with those of previous calculations which used a local field factor that satisfied the compressibility sum rule in three-dimension. In general, the stopping power increases by taking into account the short-range interactions. In addition, it is found that the dicluster stopping power (in particular the uncorrelated part) obtained from our calculations is smaller than the previous work.