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951.
Phycomyces blakesleeanus produced an abundance of sexual organs when two mating types met on solid medium, but only about 14.7% of the sexual organs
developed to the final stages. On the sexual organs showing arrested development, vegetative hyphae or dwarf sporangiophores
(microphores) often regenerated. This vegetative regeneration was accelerated when the paired and looped progametangia were
isolated from mycelia, when the counterparts of the progametangial cells constructing the loop were surgically incised, and
whenPhycomyces was mated at high temperature (25–27°C). A leaky-carotenogenic mutant, whose sexual reaction was imperfect and arrested at
an intermediate stage even when mated with the wild type, also regenerated hyphae with a high frequency on these arrested
intermediate organs. The vegetative regeneration seems to result from interruption of a cell-to-cell recognition system between
cells of different mating type, which is believed to be essential for the mating process of this fungus in addition to the
pheromonal actions. 相似文献
952.
Inhibition by secalonic acid D of oxidative phosphorylation and Ca2+-induced swelling in mitochondria isolated from rat livers. 总被引:2,自引:1,他引:1 下载免费PDF全文
The in vitro biological activity of secalonic acid D, a mycotoxin from Aspergillus ochraceus, was studied to assess its cytotoxicity for isolated rat liver mitochondria. Secalonic acid D uncoupled the oxidative phosphorylation of mitochondria and caused a mild inhibition of state 3 respiration. Secalonic acid D weakly enhanced latent ATPase activity in mitochondria but suppressed 2,4-dinitrophenol-stimulated ATPase activity. Secalonic acid D did not induce pseudoenergized swelling of mitochondria and markedly inhibited the Ca2+-induced swelling of mitochondria in KCl isotonic solution. 相似文献
953.
Y Okamura M Yamazaki T Yamaguchi Y Komoda A Sugimoto H Nakajima 《Biochimica et biophysica acta》1991,1073(3):538-542
Anti-bilirubin-IX alpha monoclonal antibodies exclusively specific for unconjugated bilirubin-IX alpha are prepared and characterized. Using modified MBS (metamaleimidobenzoyl-N-hydroxysuccinimide ester) method, bilirubin-IX alpha was covalently coupled to bovine serum albumin (BSA) retaining its intramolecular hydrogen bonds as well as three-dimensional structure. Somatic cell fusion was performed between murine spleen cells immunized with the bilirubin-IX alpha-BSA and murine myeloma P3-X63-Ag8-U1 cells. After screening assay, 58 clones were identified which were producing antibodies not to albumin nor MBS, but to haptenic bilirubin-IX alpha. In inhibition analysis, the antibodies in the culture supernatant reacted only with bilirubin-IX alpha to a varying degree, but did not react with conjugated bilirubin-IX alpha, including bilirubin-IX alpha monoglucuronide, bilirubin-IX alpha diglucuronide, and ditauronic bilirubin-IX alpha. 相似文献
954.
The conformations of cis and trans cyclic retro-inverso dipeptides--2-[(4-hydroxy)benzyl]-5-benzyl-4,6(1H,2H,3H,5H)-pyrimidinedi one (c[mTyr-gPhe]), and 2-benzyl-5-amino-5-[(4-hydroxy)benzyl]-4,6(1H,2H,3H,5H)-pyrimidinedione (c[mTyr-gPhe]), and 2-benzyl-5-amino-5-[(4-hydroxy)benzyl]-4,6(1H,2H,3H,5H)-pyrimidinedione (c[(alpha-amino)mTyr-gPhe])--and the parent cyclic dipeptides--c[tyrosyl-phenylalanine] (cis-c[L-Tyr-L-Phe]) and c[tyrosyl-D-phenylalanine] (trans-c[L-Tyr-D-Phe])--were studied by using 1H-nmr spectroscopy and semiempirical energy calculations. In the cis compounds of all the cyclic retro-inverso and parent dipeptides, the most stable conformer has both aromatic side chains sharing the space over the backbone ring in a "face-to-face" fashion. All the trans compounds predominantly assume a "sandwich" conformation in which the two aromatic rings are folded back over the backbone ring on opposite sides. However, different conformational preferences were observed for the backbones between the retro-inverso and parent cyclic dipeptides. The parent cyclic dipeptide trans-c[L-Tyr-D-Phe] adopts two types of boat structures with different side-chain orientations in almost equal amounts: one with the Tyr side chain in a pseudoaxial position and the Phe side chain in a pseudoequatorial position, the other with the Tyr side chain in a pseudoequatorial position and the Phe side chain in a pseudoaxial position. On the other hand, the cyclic retro-inverso dipeptides trans-c[mPhe-gTyr] and trans c[mTyr-gPhe] assume only one type of boat structure in which the malonyl side chain is in a pseudoequatorial and the gem-diamino side chain is in a pseudoaxial position. In addition to the preferred conformations, the conformational energies of the C alpha--C beta bonds in the malonyl and gem-diamino residues were estimated from the temperature variation of vicinal 1H--1H coupling constants for the H--C alpha--C beta--H groupings observed for the trans isomers of cyclic retro-inverso dipeptides. The energies were evaluated to be 1.1 and 1.8 kcal mol-1 for the malonyl and gem-diamino residues, respectively. Applying these energies to the parent cyclic dipeptide trans-c[L-Tyr-D-Phe], the observed fractions of three side-chain conformations are reasonably reproduced. The conformational energies as well as conformational properties of the molecules estimated in this investigation may be useful to refine force constants for both parent and retro-inverso peptides with aromatic side chains. 相似文献
955.
Mass production of human epidermal growth factor using fed-batch cultures of recombinant Escherichia coli 总被引:2,自引:0,他引:2
Shimizu N Fukuzono S Harada Y Fujimori K Gotoh K Yamazaki Y 《Biotechnology and bioengineering》1991,38(1):37-42
Fed-batch cultures of recombinant E. coli HB101 harboring expression plasmid pTRLBT1 or pTREBT1, with acetate concentration monitoring, are investigated to obtain high cell density and large amounts of human epidermal growth factor (hEGF). The expression plasmid pTRlBT1 contains a synthetic hEGF gene attached downstream of the N-terminal fragment of the trp L gene preceded by the trp promoter. The expression plasmid pTREBT1 contains the same coding sequence attached downstream of the N-terminal fragment of the trp E gene preceded by the trp promoter, trp L gene, and attenuator region. E. coli harboring pTREBT1 produces 0.56 mg/L hEGE and immediately degrades it. On the other hand E. coli harboring pTRLBT1 produces 6.8 mg/L hEGF and does not decompose it. Prominent inclusion bodies are observed in E. coli cells harboring pTRLBT1 using an election microscope. To Cultivate E. coli harboring pTRLBT1, a fed-batch culture system, divided into a cell growth step and an hEGF production step, is carried out. The cells grow smoothly without acetate-induced inhibition. Cell concentration and hEGF quantity reach the high values of 21 g/L and 60 mg/L, respectively. 相似文献
956.
957.
N Todoroki Y Watanabe T Akaike Y Katagiri K Tanoue H Yamazaki T Tsuji S Toyoshima T Osawa 《Biochemical and biophysical research communications》1991,179(2):756-761
We have examined the effect of inflammatory cytokines on the platelet activation. IL-1 beta and IFN-gamma were found to enhance the adhesion of thrombin-treated platelets to monocytic leukemia cells (U937), when the adhesion was assayed by platelet-mediated cell agglutination. The agglutination was inhibited by a monoclonal anti-GMP140 antibody or EDTA, suggesting that the enhanced platelet adhesion to the leukemic cells was mediated by GMP140. In addition, these cytokines also increased the release of 5-HT from platelets in the presence of a low concentration of thrombin. These data suggest that platelet functions are regulated by the cytokines and that activated platelets participate in inflammatory process. 相似文献
958.
The assignments of individual magnetic resonances of backbone nuclei of a larger protein, ribonuclease H from Escherichia coli, which consists of 155 amino acid residues and has a molecular mass of 17.6 kDa are presented. To remove the problem of degenerate chemical shifts, which is inevitable in proteins of this size, three-dimensional NMR was applied. The strategy for the sequential assignment was, first, resonance peaks of amides were classified into 15 amino acid types by 1H-15N HMQC experiments with samples in which specific amino acids were labeled with 15N. Second, the amide 1H-15N peaks were connected along the amino acid sequence by tracing intraresidue and sequential NOE cross peaks. In order to obtain unambiguous NOE connectivities, four types of heteronuclear 3D NMR techniques, 1H-15N-1H 3D NOESY-HMQC, 1H-15N-1H 3D TOCSY-HMQC, 13C-1H-1H 3D HMQC-NOESY, and 13C-1H-1H 3D HMQC-TOCSY, were applied to proteins uniformly labeled either with 15N or with 13C. This method gave a systematic way to assign backbone nuclei (N, NH, C alpha H, and C alpha) of larger proteins. Results of the sequential assignments and identification of secondary structure elements that were revealed by NOE cross peaks among backbone protons are reported. 相似文献
959.
M Nakamura I Yamazaki T Kotani S Ohtaki 《The Journal of biological chemistry》1989,264(22):12909-12913
The one- or two-electron oxidation of thyroglobulin by the thyroid peroxidase system was found to be regulated by the iodine content of thyroglobulin. The catalytic intermediate of thyroid peroxidase observed at steady state of the reaction was Compound I and II when the iodine content in thyroglobulin was 0.2 and 0.7%, respectively, apparent rate constants for the rate-limiting steps being estimated at 4.7 x 10(7) and 4.8 x 10(4) M-1 S-1. The thyroglobulin-mediated oxidation of GSH occurred by way of two-electron transfer at 0.2% iodine content and by way of one-electron transfer at 0.7% iodine content. The spin-trapping experiment with 5,5-dimethyl-1-pyrroline-N-oxide showed that glutathione radicals were formed in the latter reaction but not in the former. In the reactions of thyroid peroxidase, the one- and two-electron oxidations of ascorbate were also mediated by 0.2 and 0.7% iodine thyroglobulins, respectively. The reactions were analyzed and mimicked with the use of p-cresol and p-acetaminophenol as a mediator in the reactions of lactoperoxidase and thyroid peroxidase. 相似文献
960.
The side chain conformations of α-helical poly(L -glutamic acid) esters $ \rlap{--}[NHCH(CH_2 CH_2 COOR)CO\rlap{--}]_x $, carrying a homologous series of ester residues such as R = ? (CH2)n? with n = 1–3, have been studied in the lyotropic liquid crystalline state (chloroform 20 v/v%) by the deuterium nmr method. In order to study the surface chirality of the molecule, the phenyl groups situated at the terminal of the side chain have been deuterated. From the observed deuterium quadrupolar splittings, the average inclination θp of the para-axis of the phenyl group with respect to the α-helical backbone was elucidated. A distinct odd–even oscillation in the quantity such as 〈 cos2 θp〉 was observed with the number of methylene units n. A rotational isomeric state analysis has indicated that the observed orientational correlation arises from the interdependence of the neighboring bond rotation along the side chain. Preference of the “extended” conformations is also enhanced by the mutual conformational exclusion of neighboring side chains. 相似文献