Preferred conformations of cyclic Ac-Cys-Pro-Xaa-Cys-NHMe peptides: A model for chain reversal and active site of disulfide oxidoreductase

The conformational study on cyclic Ac-Cys-Pro-Xaa-Cys-NHMe (Ac-CPXC-NHMe; X=Ala, Val, Leu, Aib, Gly, His, Phe, Tyr, Asn and Ser) peptides has been carried out using the Empirical Conformational Energy Program for Peptides, version 3 (ECEPP/3) force field and the hydration shell model in the unhydrated and hydrated states. This work has been undertaken to investigate structural implications of the CPXC sequence as the chain reversal for the initiation of protein folding and as the motif for active site of disulfide oxidoreductases. The backbone conformation DAAA is commonly the most feasible for cyclic CPXC peptides in the hydrated state, which has a type I β-turn at the Pro-Xaa sequence. The proline residue and the hydrogen bond between backbones of two cystines as well as the formation of disulfide bond appear to play a role in stabilizing this preferred conformation of cyclic CPXC peptides. However, the distributions of backbone conformations and β-turns may indicate that the cyclic CPXC peptide seems to exist as an ensemble of β-turns and coiled conformations in aqueous solution. The intrinsic stability of the cyclic CPXC motif itself for the active conformation seems to play a role in determining electrochemical properties of disulfide oxidoreductases. © 2003 Elsevier B.V. All rights reserved

Influence of the antibody purification method on immunoassay performance: Hapten-antibody binding in accordance with the structure of the affinity column ligand

The effects of ligands for immunoaffinity chromatography on the immunoassay were investigated with three goat anti-methamphetamine (anti-MA) antibodies (Abs). An N-4-aminobutyl derivative of methamphetamine (4-ABMA) was conjugated with proteins and used as immunogens. All the antisera produced were purified by affinity chromatography with various ligands of 4- ABMA-proteins and of haptens as well as protein G: 4-ABMA-bovine serum albumin (4-ABMA-BSA), 4-ABMA-keyhole limpet hemocyanine (4-ABMA-KLH), 4-ABMA- ovalbumin (4-ABMA-OVA), MA, 4-ABMA, and amphetamine were used as ligands. Enzyme-linked immunosorbent assay (ELISA) was conducted to examine characteristics of the purified Abs with the 4-ABMA-OVA competitor coated. The results obtained revealed that characters of the purified Abs were closely related with chemical structures of ligands used. The Abs from the MA and the amphetamine columns showed better sensitivities than those from the others in each antiserum. Particularly, the Ab from the amphetamine column gave the best resuits in terms of sensitivity and specificity. The recognition or the affinity of the Ab selected was considered to be affected by the structure of the ligand concerned. These results suggest that the Ab purification method should be considered as an important parameter which has great influence on the performance of immunoassays with polyclonal Abs

Effect of recombinant bovine somatotropin (rBST) administration on residual BST and insulin-like growth factor-I levels in various tissues of cattle

This study was performed to investigate the effects of recombinant bovine somatotropin (rBST) administration on residual BST and insulin-like growth factor-I (IGF-I) levels in various tissues. Two experiments, (A) and (B) were conducted as follows. (A)Beef cattle (average b.w. of 450 kg) were divided into three groups control (CONT), low-dose (LOW) and high-dose HIGH groups. The CONT group received nether rBST nor vehicle. The LOW and HIGH groups were treated for 20 weeks by s.c injection with 250 mg rBST at one- week intervals and 500 mg rBST at two-week intervals, respectively. (B) Beef cattle were divided into four groups: control, (CONT) group, as described in experiment (A), and sustained-release, low-dose (SR-L), sustained-release, medium-dose (SR-M) and sustained-release, high-dose (SR-H) groups. SR-L, SR- M and SR-H were treated at two-week intervals for 24 weeks by s.c. injection with doses of 0.42 mg rBST/kg b.w. (0.08 mg rBST/kg b.w./day), 0.84 mg rBST/kg b.w. (0.06 mg rBST/kg, b.w./day) and 1.26 mg rBST/kg b.w. (0.09 mg rBST/kg b.w./day), respectively. In both experiments, animals were killed two weeks after the final treatment. In experiment A residual BST and IGF-I levels in muscle tissues of the LOW and HIGH groups were not affected by rBST administration. In experiment (B) residual BST and IGF-I levels in muscle fat liver and kidney tissues of treated groups were not different from that of the CONT group either. These results suggest that levels of BST and IGF-I n various tissues are not increased at two weeks after rBST administration

Preferred conformations of RDGX tetrapeptides to inhibit the binding of fibrinogen to platelets

The conformational study on Arg-Gly-Asp (RGD)-containing tetrapeptides in the unhydrated and hydrated states has been carried out using the force field ECEPP/3 and the hydration shell model. The tetrapeptides studied here are H-RGDX-OH (X = Trp, Tyr, Phe, Leu, Val, Cys, Gln, and Ser), which show the inhibitory activity for binding of fibrinogen to platelets in the order of RGDW ≈ RGDY ≈ RGDF ≈ RGDL > RGDV ≥ RGDC ≥ RGDQ ≥ RGDS. The backbone conformations with two C7 backbone-to-backbone hydrogen bonds between Asp and Arg residues and between Xaa and Gly residues are in common most probable for the RGD sequence of RGDX tetrapeptides in the hydrated state. The dominant β-turns for RGDX are found to be the types V' and IV at Gly-Asp and Asp-Xaa sequences, respectively, which are quite similar to the types II' and I (or II), respectively. However, it cannot be ruled out that the extended conformations are also remarkably feasible for RGDX tetrapeptides in water by peering the distributions of backbone conformations. These calculated results are consistent with the experimental results on RGD-containing proteins and conformationally constrained RGD-containing peptides. The reason why the RGDX becomes more potent as the side chain of the X residue is more hydrophobic may be ascribed to that the more hydrophobic is the residue X, the more populated are β-turn structures for the Gly-Asp sequence. The hydrophobic side chain of X residue exposed to water is likely to interact with the hydrophobic region of receptor easily. © 2002 Wiley Periodicals, Inc

The Coping process of family caregivers for demented elderly at home

학위논문(박사)--서울대학교 대학원 :간호학과 간호학 전공,2001.Docto

Homology modeling and molecular docking study of translationally controlled tumor protein and artemisinin

Translationally controlled tumor protein (TCTP), also known as histamine releasing factor (HRF), is found abundantly in different eukaryotic cell types. The sequence homology of TCTP between different species is very high, belonging to the MSS4/DSS4 superfamily of proteins. TCTP is involved in both cell growth and human late allergy reaction, as well as having a calcium binding property; however, its primary biological functions remain to be clearly elucidated. In regard to many possible functions, the TCTP of Plasmodium falciparum (Pf) is known to bind with an antimalarial agent, artemisinin, which is activated by heme. It is assumed that the endoperoxide-bridge of artemisinin is opened up by heme to form a free radical, which then eventually alkylates, probably to the Cys14 of PfTCTP. Study of the docking of artemisinin with heme, and subsequently with PfTCTP, was carried out to verify the above hypothesis on the basis of structural interactions. The three dimensional (3D) structure of PfTCTP was built by homology modeling, using the NMR structure of the TCTP of Schizosaccharomyces pombe as a template. The quality of the model was examined based on its secondary structure and biological function, as well as with the use of structure evaluating programs. The interactions between artemisinin, heme and PfTCTP were then studied using the docking program, FlexiDock. The center of the peroxide bond of artemisinin and the Fe of heme were docked within a short distance of 2.6Å, implying the strong possibility of an interaction between the two molecules, as proposed. When the activated form of artemisinin was docked on the PfTCTP, the C4-radical of the drug faced towards the sulfur of Cys14 within a distance of 2.48Å, again suggesting the possibility of alkylation having occurred. These results confirm the proposed mechanism of the antimalarial effect of artemisinin, which will provide a reliable method for establishing the mechanism of its biological activity using a molecular modeling study

Study on the molecular weights of radioprotective ginseng proteins by HPLC method

Partially purified ginseng proteins were either treated with sodium dodecyl sulfate (SDS) and β-mercaptoethanol to denature the proteins or not, and subjected to Thin Layer Chromatography (TLC) and High Performance Liquid Chromatography (HPLC) to compare the components of each fraction. Standard proteins of known molecular weights (MW) were also either treated with SDS and β-mercaptoethanol or not, and subjected to HPLC to obtain regression lines for MW determination. From the retention times obtained from samples in either case by HPLC, the MW were estimated as following. In SDS treated condition, GI fraction showed three peaks each with MW of above 100,000, 51,000 and 19,000. GII showed one original peak with MW of 21,000 and GIII, two peaks each with MW of 19,000 and 14,000. On the other hand, in non-SDS treated condition, GI fraction showed two peaks each with MW of above 200,000 and 52,000. GII showed one original peak with MW of 41,000 and GIII, three peaks each with MW of 28,000, 19,000 and 14,000. © 1986 The Pharmaceutical Society of Korea

Effects of radioprotectors on DNA repair capacity of tumor cells

Three cell lines, CHO, L929 and B16 which are non-tumorigenic, tumorigenic and cancer cells, respectively, were first tested for their survival in the presence of radioprotective ginseng protein fraction(GPF). The influence of three radioprotectors-GPF, cysteamine, and 1-Methyl-2-bis[(2- methylthio)vinyl] quinolinium iodide (MVQI) on DNA repair capacity of UV damaged cells was also investigated by measuring 3H-thymidine incorporation of PUVA treated cells. In cell survival test, the GPF showed higher cytotoxicity in L929 and B16 than in CHO cells. However, the degree of cell killing was not high enough to consider it as an antitumorigenic agent. Variable results were obtained in the effects on DNA repair capacity depending on the protectors and cell lines used. In pretreatment, the presence of GPF and MVQI brought about a significant increase in the capacity in both CHO and B16 cells. However, in L929, the enhancing effect was not shown. In all three cell lines, cysteamine showed lower repair capacity than control, suggesting the primary damage reduction to occur, rather than repair enhancement. In posttreatment, GPF and MVQI resulted in stronger enhancing effects in L929 and B16 cells, while it was weaker in CHO cells. Here also cysteamine showed a very little or no increase in the capacity in all three cell lines. These results demonstrate that GPF has mild cytotoxicity in tumorigenic cells and that GPF and MVQI enhance DNA repair capacity of UV damaged cells, whether they are tumorigenic or not. On the other hand, cysteamine shows only damage reduction effect. Cells of different genetic origin seem to give different responses to the modifier and different modifiers may possibly work by different mechanisms