In the present work, an extensive theoretical calculation study on HISTIDINE-HISTIDINE dipeptide in gas phase is done by using DFT method with Gaussian 98 program. Through investigations on the molecular geometries of this molecule it is found that there is six rings in the molecules not two rings. The presence of four intramolecular hydrogen bonds is responsible for the formation of additional four rings besides two imidazole rings which gives more stability to the molecule. The quantum theory of atoms in molecules (QTAIM) proves these strong intramolecular hydrogen bonds in the title dipeptide.

Enzymes as drugs have two important features that distinguish them from all other types of drugs. First, enzymes often bind and act on their targets with great affinity and specificity. Second, enzymes are catalytic and convert multiple target molecules to the desired products. These two features make enzymes specific and potent drugs that can accomplish therapeutic biochemistry in the body that small molecules cannot. These characteristics have resulted in the development of many enzyme drugs for a wide range of disorders. Urate oxidase or uricase catalyzes oxidation of uric acid to alantoin which can be produced as a recombinant enzyme drug for treatment of hyperuricemia. The inherent poor stability of this enzyme is known to limit its efficacy, So that, stabilization of this enzyme is considered.There are a lot of factors that influence proteins stability; recent studies have shown that His-His interactions could have be an important role in stability and activity of proteins. For this purpose, we used site-directed mutagenesis (SDM) to substitute Gly 267 with His, Ala and Pro. Purified variants were biochemically characterized and compared with the wild type. Results revealed considerable changes in the catalytic efficiency, thermal stability and tertiary structures.

Hepatitis B virus (HBV) is considered a global health problem whid. affects 360 millions of people worldwide and about two millions in Iran. Among HBV antigens, the physiological function of HBeAg is still unresolved. In this respect, its presence in positive patients is regarded as a marker of viral replication and it may have roles in pathogenesis and persistence of the disease, while no obvious changes in clinical course of the disease has been observed in negative patients. As a result, availability of this protein with characteristics of the naturally occurred antigen in high amounts and of the same purity is highly required for being. Utilized in medical research and diagnosis. At present, recombinant HBeAg is being produced in different expression systems for various applications. In the present study, by application of a simple expression/purification system in E. coli and with the aim of producing physiologically natural HBeAg, that portion of the gene, which exactly corresponds to amino acid sequence of the blood-borne HBeAg have been isolated and cloned into pQE-30 vector which adds a 6x Histag to the N-terminal of the inserted gene, providing the ability of one step purification method by exploiting Ni-NTA column chromatography. Following restriction analysis and confirmation of recombinant vector accuracy, transformation to E. coli M15 cells and IPTG-mediated induction for protein expression was performed. Analysis of the purified protein by SOS-PAGE, ELISA and Western blotting indicated that obtained recombinant HBeAg had the perfect antigenic properties of authentic HBeAg and addition of the His-tag segment which produces extra epitopes on this antigen had no adverse effect on these properties. The results of this study clearly describe a very simple and efficient system for providing recombinant HBeAg in high yield and purity for diagnostic and physiological research applications.

Introduction: Thioperamide, an histamin H3 receptor antagonist, blocks histamine release from the histaminergic, presynapse, thus affecting histamine and its metabolite levels in the brain and being able to modify activity of the histaminergic neuron system. The multiple function of histamin as a chemical messenger in cell to cell communication have been progressively reveals. Histamine is stored in, and released from, various cellular populations including immunoglobulin E receptor bearing cells, endocrine cells and neurons in the central or peripheral nervous system. HISTIDINE decarboxylase (E.C.4.1.1.22) the enzyme which forms histamine in mammalian tissues.Method & Material: A simple method for the assay of HISTIDINE decarboxylase activity in brain tissue was studied. Rats were injected with saline or thioperamide (50 micro g/Kg) i.p.. One hour later, the animal was scarified and the brain was homogenate. The supernatant of homogenates was placed in tube and centrifuge at 4500 *g for 30 min. The activity of HISTIDINE decarboxylase was assayed by measuring the histamine formed spectrophotometer by the reaction with 2,4,6-trinitrobenzene sulfonate at 420 nm.Results & Discussion: Results show that the enzyme activity was highest in the hypothalamus, lower in the cerebrum. The brain HISTIDINE decarboxylase activity was decreased by thioperamide 1 hr after administration in the thalamus and cerebrum.

HISTIDINE at the doses 30 and 60ml/kg had no effect when injected at 7:00h, or at 19:00h. HISTIDINE at the doses of 120, 240 and 480 mg/kg decreased defecation at the first 8 and 24 hours post injection, respectively, when injected at 07:00h. The amino acid at the doses of 120, 240 and 480 mg/kg decreased the number of fecal pellets at 2, 8 and 24 h post injection, respectively, when injected at 19:00h. Suppressive effect of HISTIDINE in the light period was more intense and lasted longer than that in the dark period. The mean number of pellets for each individual prior to the interventional study was recorded as interval negative control.