共查询到20条相似文献,搜索用时 15 毫秒
1.
The cyclo7,10[Cys7,Cys10,Nle12], cyclo7,10[Cys7,D -Ala9,Cys10,Nle12], and cyclo7,10[Cys7,L -Ala9,Cys10,Nle12] analogues of the α-factor mating pheromone (WHWLQLKPGQPMY) of the yeast Saccharomyces cerevisiae were studied in DMSO/water (80 : 20) and aqueous solution by nmr spectroscopy. In addition, the cyclo7,10[Cys7,D -Val9,Cys10,Nle12] α-factor was examined in DMSO/water. Nuclear Overhauser effect (NOE) and NH dδ/dT data indicate that the cyclo7,10[Cys7,D -Val9,Cys10,Nle12] α-factor adopts a type II β-turn in DMSO/water and that the cyclo7,10[Cys7,D -Ala9,Cys10,Nle12] - and cyclo7,10-[Cys7,L -Ala9,Cys10,Nle12] α-factor analogues adopt type II and type I/III β-turns, respectively, in both DMSO/water and aqueous solutions. In aqueous solution, residues 8 and 9 of the cyclo7,10[Cys7,Cys10,Nle12] α-factor appear to adopt at least two distinct conformations, one of these being identified as a type I/III β-turn. In contrast, the cyclo7,10[Cys7,Cys10,Nle12] α-factor appears to adopt predominately a type II β-turn in DMSO/water. Quantitative NOE measurements of the cyclo7,10[Cys7,Cys10,Nle12]-, cyclo7,10[Cys7,D -Val9,Cys10,Nle12]-, and cyclo7,10[Cys7,L -Ala9,Cys10,Nle12] α-factors in DMSO/water were used to derive three-dimensional structures of the cyclo7,10[Cys7,Pro8,X9Cys10] portion of these analogues. © 1994 John Wiley & Sons, Inc. 相似文献
2.
Yoshio Ikeda Kazuwa Nakao Takaaki Yoshimasa Noboru Yanaihara Shosaku Numa Hiroo Imura 《Biochemical and biophysical research communications》1982,107(2):656-662
High performance liquid chromatography (HPLC) coupled with specific radioimmunoassays for methionine-enkephalin-Arg6-Gly7-Leu8 (Met-E-Arg6-Gly7-Leu8), methionine-enkephalin (Met-E), leucine-enkephalin (Leu-E) and methionine-enkephalin-Arg6-Phe7 (Met-E-Arg6-Phe7) has demonstrated that Met-E-Arg6-Gly7-Leu8 exists together with Met-E, Leu-E and Met-E-Arg6-Phe7 in the brain of guinea pig, rat and golden hamster. The content of Met-E-Arg6-Gly7-Leu8 was comparable to those of Leu-E and Met-E-Arg6-Phe7, whereas that of Met-E was the highest among the four opioid peptides. These results are compatible with the recent studies on the nucleotide sequence of cloned cDNA for preproenkephalin from bovine adrenal medulla, which reveal that this precursor molecule contains four copies of Met-E and one copy each of Leu-E, Met-E-Arg6-Phe7 and Met-E-Arg6-Gly7-Leu8. The co-existence of Met-E-Arg6-Gly7-Leu8 with Met-E, Leu-E and Met-E-Arg6-Phe7 suggests that their biosynthetic pathway in the brain is similar to that in the adrenal medulla. 相似文献
3.
Summary The distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 (met5-enk-arg6-gly7-leu8) within the gastrointestinal tract of the rat has been determined by immunohistochemistry and radioimmunoassay by use of a newly developed antibody to met5-enk-arg6-gly7-leu8. With both techniques, met5-enk-arg6-gly7-leu8-immunoreactivity (met5-enk-arg6-gly7-leu8IR) was detected in all regions of the gastrointestinal (GI) tract except the esophagus. The highest concentration of immunoreactive met5-enk-arg6-gly7-leu8 was observed in the colon, while intermediate concentrations were found in the stomach, duodenum, jejunum, and ileum. Immunostained somata were observed chiefly in the myenteric plexus; immunostained processes were present primarily in the myenteric plexus and the circular muscle layer. This distribution pattern is similar to that previously observed with antiserum to met5-enkephalin-arg6-phe7 (met5-enk-arg6phe7). Chromatographic analysis of met5-enk-arg6-gly7leu8-immunoreactive peptides extracted from the GI tract revealed the presence of an immunoreactive peptide of high molecular weight which accounted for approximately three-quarters of met5-enk-arg6-gly7-leu8-IR in both stomach and colon. These findings suggest a role for peptides related to the octapeptide met5-enk-arg6-gly7-leu8 in the regulation of GI function. 相似文献
4.
Two nonadeoxynucleotides with the sequences, d-C-T-A-A-G-G-G-A-G (nonanucleotide-I) and d-T-C-T-C-C-G-G-T-T (nonanucleotide-II), and a heptadeoxynucleotide having the sequence, d-A-G-A-G-T-C-T, have been chemically synthesized. These polynucleotides represent, respectively, the nucleotide sequences 22 to 30, 41 to 49, and 28 to 34 of the gene for yeast alanine transfer RNA (Fig. 1). The synthetic steps used in the synthesis of the nonanucleotide-I were: the condensation of the protected nucleoside, d-MMTr-CAn, with the protected nucleotide, d-pT-OAc, to give the dinucleotide, d-MMTr-CAnpT; the condensation of the dinucleotide with d-pABz-OAc to give the trinucleotide, d-MMTr-CAnpTpABz; the condensation of the latter with the dinucleotide, d-pABzpG1B-OAc, to give the pentanucleotide, d-MMTr-CAnpTpABzpABzpG1B; the condensation of this pentanucleotide with d-pG1BpG1B-OAc to give the protected heptanucleotide, d-MMTr-CAnpTpABzpABzpG1BpG1BpG1B, and finally, the condensation of this heptanucleotide with the dinucleotide, d-pABzpG1B-OAc, to give the protected nonanucleotide, d-MMTr-CAnpTpABzpABzpG1BpG1BpG1BpABzpG1B. The steps used in the synthesis of the nonanucleotide-II were: the condensation of d-MMTr-T with the tetranucleotide, d-pCAnpTpCAnpCAn-OAc, to give the pentanucleotide, d-MMTr-TpCAnpTpCAnpCAn; the condensation of the latter with the dinucleotide, d-pG1BpG1B-OAc, to give the heptanucleotide, d-MMTr-TpCAn-pTpCAnpCAnpG1BpG1B, and finally, the condensation of the heptanucleotide with the dinucleotide, d-pTpT-OAc, to give the protected deoxynonanucleotide, d-MMTr-TpCAnpTpCAnpCAnpG1BpG1BpTpT. For the synthesis of the heptanucleotide, A-G-A-G-T-C-T, the 5′-monocyanoethyl tetranucleotide, d-CEpABz-pG1BpABzpG1B, was condensed with the trinucleotide, d-pTpCAnpT-OAc, to give the protected heptanucleotide, d-pABzpG1BpABzpG1BpTpCAnpT. After removal of the N-protecting groups, the completely deprotected nonanucleotides, as well as the intermediate oligonucleotides and the heptanucleotide, d-A-G-A-G-T-C-T, were purified further by a combination of paper and column chromatography. 相似文献
5.
T Shibasaki L Deftos R Guillemin 《Biochemical and biophysical research communications》1979,90(4):1266-1273
Fifteen analogs of luliberin (2, LRH) were synthesized by the solid phase method and examined for their ability to block ovulation in the rat. Two analogs, [Ac-DAla1,DPhe2,DTrp3,6]-LRH and [Ac-DPhe1,DPhe2,DTrp3,6]-LRH, each blocked ovulation at a single injection dose of 250 μg administered at noon on the day of proestrus; three peptides, [Ac-DPro1,DPhe2,DTrp3,6]-LRH, [Ac-DThi1,DPhe2,DTrp3,6]-LRH and [Ac-DTrp1,DPhe2,DTrp3,6]-LRH, were effective at doses of 500 μg each; and four others, [Ac-DTrp1,DPhe2,DTrp3,DTrp(Nps)6]-LRH, [Chlorambucil-DPhe1, DPhe2, DTrp3,6]-LRH, [1,DThi2,DTrp3,6]-LRH and [(2-DLys6]-LRH, gave partial inhibition at doses tested. 相似文献
6.
Red blood cells (RBCs) are probably the most common target through the damaging action of reactive oxygen species on the cells. The photohemolysis activity of m-chloroperbenzoic acid (CPBA) was concentration- and exposure time-dependent. Twenty minutes photo exposure time and 200?μm of CPBA concentration were optimum to study the effect of generated superoxide (O2-) and hydroxyl (?OH) radicals on RBCs. RBCs lysis photosensitized by CPBA was investigated in the presence of [(VL2O)(VL2H2O)]Cl6, [MnL2O]2Cl42H2O, [FeL2Cl2]Cl H2O, [CoL2Cl2]4H2O or [ZnL2Cl2]H2O respectively, where L is 2-methylaminopyridine, with SOD-mimetic activities with the aim of ascertaining their protective activity towards the photo induced cell damage. The decrease of photolytic activity caused by these complexes was concentration-dependent and the maximum percentage of protective activity was 75, 70, 68, 57 or 24% for [(VL2O)(VL2H2O)]Cl6, [MnL2O]2Cl4 2H2O, [FeL2Cl2]Cl H2O, [CoL2Cl2]4H2O or [ZnL2Cl2]H2O complex respectively, against the cell irradiated without addition of metal complexes. The comparison between the decrease of photolytic activity caused by these complexes and their SOD-mimetic activity of these metal complexes showed an appreciable correlation. 相似文献
7.
Extensive conformational analysis of a series of β‐alkyl substituted cyclopeptides—cyclo(Pro1–Xaa2–Nle3–Ala4–Nle5–Pro6–Xaa7–Nle8–Ala9–Nle10) and cyclo[Pro1–Xaa2–Nle3–(Cys4– Nle5–Pro6–Xaa7–Nle8–Cys9)–Nle10] as well as their corresponding unsubstituted core structures cyclo(Pro1–Xaa2–Ala3–Ala4–Ala5–Pro6–Xaa7–Ala8–Ala9–Ala10) and cyclo(Pro1–Xaa2–Ala3–Cys4– Ala5–Pro6–Xaa7–Ala8–Cys9–Ala10) has been performed employing both the ECEPP/2 and the MAB force fields (Xaa = Gly, L ‐Ala, D ‐Ala, Aib, and D ‐Pro). Results show that (a) possible three‐dimensional structures of the cyclo(Pro1–Gly2–Lys3–Ala4–Lys5–Pro6–Gly7–Lys8–Ala9–Lys10) molecule are not limited to a single extended “rectangular” conformation with all Lys side chains oriented at the same side of the molecule; (b) conformational equilibrium in monocyclic analogues obtained by replacements of conformationally flexible Gly residues for L ‐Ala, D ‐Ala, Aib, or D ‐Pro is not significantly shifted towards the target “rectangular” conformational type; and (c) introduction of disulfide bridges between positions 4 and 9 is a very powerful way to stabilize the target conformations in the resulting bicyclic molecules. These findings form the basis for further design of rigidified regioselectively addressable functionalized templates with many application areas ranging from biostructural to diagnostic purposes. © 1999 John Wiley & Sons, Inc. Biopoly 50: 361–372, 1999 相似文献
8.
Bacillus thuringiensis produces several larvicidal crystalline inclusions during sporulation. An understanding of their mechanisms of action is
commercially important. In this study, two toxins, Cry1Ab and Cry1Ac, were compared that showed 98% amino acid identity in
domain I and II, but differed significantly in domain III. Using site-directed mutagenesis techniques, two conserved loop
2 Arg's (368RR369) of Cry1Ab and Cry1Ac toxins were replaced with Ala (368AR369, 368RA369, 368AA369), Glu (368EE369), Phe (368FF369), His (368HH369), and Lys (368KK369). The effect of these mutants on structural stability, larvicidal potency, receptor binding, and ionic permeability towards
two important cotton pests, pink bollworm (Pectinophora gossypiella) and bollworm (Helicoverpa zea) were analyzed. All seven mutants of Cry1Ab, excluding 368AR369, produced a stable protoxin, whereas for Cry1Ac all seven mutants yielded stable protoxin. Results showed that all the stable
mutants behaved similarly to the wild type on incubation with trypsin and gut extract of both insect larvae. The Cry1Ab mutants,
368AR369, 368AA369, 368FF369, and 368HH369, lost toxicity; 368EE369 had reduced toxicity; whereas the more conserved change 368KK369 retained the toxicity similar to the wild type towards P. gossypiella. Double mutants of Cry1Ac, 368AA369 and 368FF369, abolished the toxicity. Double mutant 368KK369 of Cry1Ac retained its toxicity against P. gossypiella, whereas single mutants 368AR369, 368RA369, and 368HH369 retained only reduced toxicity. All the mutants of Cry1Ab lost their toxicity against H. zea except 368KK369. In Cry1Ac single mutants, 368AR369 and 368RA369, reduction in the toxicity was observed. A double mutant of Cry1Ac, 368KK369, also retained reduced toxicity. All the other double mutants lost their toxicity. Voltage clamping experiments on H. zea midguts provided an additional evidence about the insecticidal property and inhibition of Isc across the transepithelial membrane of the insect midgut.
Received: 5 June 2000 / Accepted: 5 July 2000 相似文献
9.
Na+-ATPase of high-K+ and low-K+ sheep red cells was examined with respect to the sidedness of Na+ and K+ effects, using inside-out membrane vesicles and very low ATP concentrations (?2 μM). With varying amounts of Na+ in the medium, i.e., at the cytoplasmic surface, Nacyt+, the activation curves show that high-K+ Na+-ATPase has a higher affinity for Nacyt+ compared to low-K+. The apparent affinity for Nacyt+ is also increased by increasing the ATP concentrations in high-K+ but not low-K+. With Nacyt+ present, Na+-ATPase is stimulated by intravesicular Na+, i.e., Na+ at the originally external surface, Naext+, to a greater extent in low-K+ than high-K+. Intravesicular K+ (Kext+) activates Na+-ATPase in high-K+ but not in low-K+ vesicles and extravesicular K+ (Kcyt+) inhibits low-K+ but not high-K+ Na+-ATPase. Thus, the genetic difference between high-K+ and low-K+ is expressed as differences in apparent affinities for both Na+ and K+ and these differences are evident at both cytoplasmic and external membrane surfaces. 相似文献
10.
Danijela Krstić Katarina Krinulović Vesna Vasić 《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):469-476
Kinetics and inhibition of Na+/K+-ATPase and Mg2+-ATPase activity from rat synaptic plasma membrane (SPM), by separate and simultaneous exposure to transition (Cu2+, Zn2+, Fe2+ and.Co2+) and heavy metals (Hg2+and Pb2+) ions were studied. All investigated metals produced a larger maximum inhibition of Na+/K+-ATPase than Mg2+-ATPase activity. The free concentrations of the key species (inhibitor, MgATP2 ? , MeATP2 ? ) in the medium assay were calculated and discussed. Simultaneous exposure to the combinations Cu2+/Fe2+ or Hg2+/Pb2+caused additive inhibition, while Cu2+/Zn2+ or Fe2+/Zn2+ inhibited Na+/K+-ATPase activity synergistically (i.e., greater than the sum metal-induced inhibition assayed separately). Simultaneous exposure to Cu2+/Fe2+ or Cu2+/Zn2+ inhibited Mg2+-ATPase activity synergistically, while Hg2+/Pb2+ or Fe2+/Zn2+ induced antagonistic inhibition of this enzyme. Kinetic analysis showed that all investigated metals inhibited Na+/K+-ATPase activity by reducing the maximum velocities (Vmax) rather than the apparent affinity (Km) for substrate MgATP2-, implying the noncompetitive nature of the inhibition. The incomplete inhibition of Mg2+-ATPase activity by Zn2+, Fe2+ and Co2+ as well as kinetic analysis indicated two distinct Mg2+-ATPase subtypes activated in the presence of low and high MgATP2 ? concentration. EDTA, L-cysteine and gluthathione (GSH) prevented metal ion-induced inhibition of Na+/K+-ATPase with various potencies. Furthermore, these ligands also reversed Na+/K+-ATPase activity inhibited by transition metals in a concentration-dependent manner, but a recovery effect by any ligand on Hg2+-induced inhibition was not obtained. 相似文献
11.
The mechanism of the protective effect of Ca2+ on cellular K+ content was studied by examination of the effect of Ca2+ on efflux of the K+ analog, 86Rb+, from preloaded cells with the use of compounds which interfere with monovalent cation movements. Ca2+ decreased 86Rb+ efflux to the same extent in the presence and absence of ouabain, suggesting that Ca2+ did not alter the activity of the (Na+ + K+)-adenosine triphosphatase pump. Ca2+ exerted a similar protective effect in the presence of furosemide, an inhibitor of K+-K+ exchange, indicative that Ca2+ was not inhibiting this pathway. Since Ca2+ did not influence these pathways, it is concluded that Ca2+ exerts its primary effect by slowing passive diffusion. In support of this, Ca2+ also slowed 22Na+ efflux. In addition, ethanol-induced leakage of 86Rb+ was reversed by extracellular Ca2+, suggestive of a Ca2+-membrane phospholipid interaction. 相似文献
12.
This paper describes a [15N,1H]/[13C,1H]-TROSY experiment for the simultaneous acquisition of the heteronuclear chemical shift correlations of backbone amide 15N–1H groups, side chain 15N–1H2 groups and aromatic 13C–1H groups in otherwise highly deuterated proteins. The 15N–1H and 13C–1H correlations are extracted from two subspectra of the same data set, thus preventing possible spectral overlap of aromatic and amide protons in the 1H dimension. The side-chain 15N–1H2 groups, which are suppressed in conventional [15N,1H)-TROSY, are observed with high sensitivity in the 15N–1H subspectrum. [15N,1H]/[13C,1H]-TROSY was used as the heteronuclear correlation block in a 3D [1H,1H]-NOESY-[15N,1H]/[13C,1H]-TROSY experiment with the membrane protein OmpA reconstituted in detergent micelles of molecular weight 80000 Da, which enabled the detection of numerous NOEs between backbone amide protons and both aromatic protons and side chain 15N–1H2 groups. 相似文献
13.
We have previously reported on the biochemical properties of a Na+,K+,2Cl?-cotransport in HeLa cells and here we deal with aspects of its physiological regulation. Na+,K+,2Cl?-cotransport in HeLa cells was studied by 86Rb+ influx and 86Rb+/22Na+ efflux measurements. The effects of rat atrial natriuretic peptide (ANP), isoproterenol, and amino acids on 86Rb+ flux, mediated by the bumet-anide-sensitive Na+, K+, 2Cl?-cotransport system and the ouabain-sensitive Na+/K+-pump, were investigated. ANP reduced bumetanide-sensitive 86Rb+ influx under isotonic as well as under hypertonic conditions. Similar decrease of bumetanide-sensitive 86Rb+ influx was observed in the presence of 8-bromo-cGMP, while neither isoproterenol as a β-receptor agonist nor 8-bromo-cAMP-could alter bumetanide-sensitive 86Rb+ influx. Furthermore, efflux of 86Rb+ and 22Na+ was greatly reduced in the presence of bumetanide and ANP. Together with our recent findings, showing functionally active, high affinity receptors for ANP on HeLa cells (Kort and Koch, Biochim. Biophys. Res. Commun. 168:148–154, 1990), this study indicates that ANP participates in the regulation of the Na+, K+, 2Cl?-cotransport system in HeLa cells. Further measurements revealed that amino acids as present in the growth medium (Joklik's minimal essential medium) and the amino acid derivative α-methyl-aminoisobutyric acid (metAlB, 1 and 5 mM, respectively) also reduced Na+, K+, 2Cl?-cotransport-mediated 86Rb+ uptake and diminished the stimulatory effect of hypertonicity on the cotransporter. In addition, the Na+/K+-pump was markedly stimulated in the presence of amino acids, while neither ANP and 8-Br-cGMP nor isoproterenol and 8-Br-cAMP had a significant effect on the activity of the Na+/K+-pump. 相似文献
14.
The activation of desoxyribonuclease on desoxyribonucleate, known to occur with Mg++ and Mn++, has been shown to occur equally well with Co++, to nearly the same extent with Fe++, and to a lesser extent with Ca++, Ba++, Sr++, Ni++, Cd++, and Zn++. The conditions under which the optimal activation is revealed vary among these ions. Thus, Mg++, Mn++, and Co++ may show marked activation under conditions in which Fe++ is nearly ineffective. Since too high a concentration of an ion may be as ineffective as too little, concentration-activation curves were determined for each ion. Per micromole of nucleic acid phosphorus, the optimal effective amount of each ion in micromoles is as follows: Mg++ 3, Mn++ 3, Co++ 3, Fe++ 0.3, Ni++ 0.3, Ba++ 1.7, Ca++ 3, Sr++ 3, Zn++ 0.3, and Cd++ 0.3.The optimum pH for the activation with Mg++, Co++, and Ca++ is about 6.5, that with Fe++ is at 5.7, while Mn++ shows two optima at pH 6.8 and 8.0.Experiments conducted in Pyrex and in quartz vessels showed the same results, and indicated that there was no activation of desoxy-ribonuclease in the absence of added salts. 相似文献
15.
Luowei Li Francis H. Kruszewski Kari Punnonen Robert W. Tucker Stuart H. Yuspa Henry Hennings 《Journal of cellular physiology》1993,154(3):643-653
Primary mouse keratinocytes in culture are induced to terminally differentiate by increasing extracellular Ca2+ concentrations (CaO) from 0.05 mM to ≥ 0.1 mM. The addition of Sr2+ (≥ 2.5 mM) to medium containing 0.05 mM Ca2+ induces focal stratification and terminal differentiation, which are similar to that found after increasing the CaO to 0.12 mM. Sr2+ in 0.05 mM Ca2+ medium induces the expression of the differentiation-specific keratins, keratin 1 (K1), keratin 10 (K10), and the granular cell marker, filaggrin, as determined by both immunoblotting and immunofluorescence. Sr2+ induces the expression of those differentiation markers in a dose dependent manner, with an optimal concentration of 5 mM. In the absence of Ca2+ in the medium, the Sr2+ effects are reduced, and Sr2+ is ineffective when both Ca2+ and serum are deleted from the medium. Sr2+ treatment increases the ratio of fluorescence intensity of the intracellular Ca2+ sensitive probe, fura-2, indicating an associated rise in the level of intracellular free Ca2+ and/or Sr2+. At doses sufficient to induce differentiation, Sr2+ also increases the level of inositol phosphates in primary keratinocytes within 30 min. The uptake curves of 85Sr2+ by primary keratinocytes are similar to those of 45Ca2+. At low concentrations, the initial uptake of both 45Ca2+ and 85Sr2+ reaches a plateau within 1 hr; at higher concentrations, the uptake of both 45Ca2+ and 85Sr2+ increases continuously for 12 hr. In keratinocytes pre-equilibrated with 45Ca2+ in 0.05 mM Ca2+ medium, Sr2+ causes an increase of 45Ca2+ uptake, which is dependent on the presence of serum. These results suggest that Sr2+ utilizes the same signalling pathway as Ca2+ to induce keratinocyte terminal differentiation and that Ca2+ may be required to exert these effects. © 1993 Wiley-Liss, Inc. 相似文献
16.
Summary 2-Aminopurine, 2-amino-N6-hydroxyadenine, 2-amino-N6-methoxyadenine and 2-amino-N6-methyl-N6-hydroxyadenine (but not N4-hydroxycytidine), strong mutagens of base analog type, may induce the SOS response in E. coli cells. This ability is greatly enhanced in dam3 mutants and abolished in dam3mutS, dam3mutH, and dam3mutL strains, thereby suggesting that the mismatch repair system is involved in the mechanism of induction.Abbreviations n2Pur
2-aminopurine
- n2oh6Ade
2-amino-N6-hydroxyadenine
- n2om6Ade
2-amino-N6-methyoxyadenine
- n2-m6oh6Ade
2-amino-N6-methyl-N6-hydroxyadenine
- oh4Cyd
N4-hydroxycytidine
- MC
mitomycin C 相似文献
17.
Summary Several enzyme polymorphisms and hemoglobin variants were typed in a sample of n=219 non-related Greek blood-donors. The following gene frequencies were observed: pa=0.201, pb=0.701, pc=0.098; PGDA=0.985, PGDc=0.015; AK1=0.942, AK2=0.058; HbA=0.988, HbS=0.012. No polymorphic variation was seen in LDH, s-MDH, PHI, or SOD. The population genetical aspects of these results are discussed.
Zusammenfassung An einer Stichprobe von n=219 erwachsenen griechischen Blutspendern wurden verschiedene Enzympolymorphismen und Hämoglobinvarianten untersucht. Folgende Genfrequenzen konnten beobachtet werden: pa=0,201, pb=0,701, pc=0,098; PGDA=0,985, PGDc=0,015; AK1=0,0942, AK2=0,058; HbA=0,988, HbS=0,012. Keine polymorphe Variation wurde bei LDH, s-MDH, PHI und SOD gefunden. Die populationsgenetischen Aspekte dieser Befunde werden diskutiert.相似文献
18.
Ichizo Shinoda Akira Fushimi Hironobu Kato Hideo Okai Sakuzo Fukui 《Bioscience, biotechnology, and biochemistry》2013,77(9):2587-2596
The primary structure of bovine β-casein contains the partial sequence of -Pro196-Val-Leu-Gly-Pro-Val-Arg-Gly-Pro-Phe-Pro-Ile-Ile-Val209 in the C-terminal portion. We previously reported that the synthetic C-terminal octapeptide, Arg202-Val209, is extremely bitter with its threshold value 0.004 mm, 250 times as strong as that of caffeine. To further investigate the bitter taste of the C-terminal portion of β-casein, we synthesized the C-terminal tetradecapeptide, Pro196-Val209, and some of its fragments. A hydrophobic hexapeptide, Pro196-Val201, was twice as bitter as caffeine. The bitter taste of the decapeptide, Pro200-Val209, was the same as that of Arg202-Val209. Although the tetradecapeptide, Pro196-Val209, was composed of two bitter peptides, Pro196-Val201 and Arg202-Val209, its bitter taste was weaker than that of Arg202-Val209 and its threshold value was 0.015 mm. We suggested that the increase of bitterness in peptides through the introduction of hydrophobic amino acids depended on the number of hydrophobic amino acids added. In addition, the synthetic retro analog of Arg202-Val209 (H-Val-Ile-Ile-Pro-Phe-Pro-Gly-Arg-OH) was not as bitter as Arg202-Val209. This indicated that the sequence of Arg202-Val209 is important for extreme bitterness. 相似文献
19.
《International journal of radiation applications and instrumentation. Part B, Nuclear medicine and biology》1987,14(2):143-151
Tumor uptake rates, concentrations in mitochondrial fraction (containing lysosome) of liver and tumors, avid accumulations in connective tissue (especially inflammatory tissue) and binding substances in these tissues for 46Sc3+ and 51Cr3+ were essentially similar to those for 67Ga3+, 111In3+, 169Yb3+, 167Tm3+, 95Zr4+ and 181Hf4+. However, the main binding substance of 46Sc3+ and 51Cr3+ in tumor and liver was the acid mucopolysaccharide (as described concerning 95Zr and 181Hf) whose molecular weight exceeded 40,000, although the main binding substance of 67Ga3+, 111In3+, 169Yb3+ and 167Tm3+ was the acid mucopolysaccharide with a molecular weight of about 10,000. 相似文献
20.
L-type Ca2+ channels select for Ca2+ over sodium Na+ by an affinity-based mechanism. The prevailing model of Ca2+ channel permeation describes a multi-ion pore that requires pore occupancy by at least two Ca2+ ions to generate a Ca2+ current. At [Ca2+] < 1 μM, Ca2+ channels conduct Na+. Due to the high affinity of the intrapore binding sites for Ca2+ relative to Na+, addition of μM concentrations of Ca2+ block Na+ conductance through the channel. There is little information, however, about the potential for interaction between Na+ and Ca2+ for the second binding site in a Ca2+ channel already occupied by one Ca2+. The two simplest possibilities, (a) that Na+ and Ca2+ compete for the second binding site or (b) that full time occupancy by one Ca2+ excludes Na+ from the pore altogether, would imply considerably different mechanisms of channel permeation. We are studying permeation mechanisms in N-type Ca2+ channels. Similar to L-type Ca2+ channels, N-type channels conduct Na+ well in the absence of external Ca2+. Addition of 10 μM Ca2+ inhibited Na+ conductance by 95%, and addition of 1 mM Mg2+ inhibited Na+ conductance by 80%. At divalent ion concentrations of 2 mM, 120 mM Na+ blocked both Ca2+ and Ba2+ currents. With 2 mM Ba2+, the IC50 for block of Ba2+ currents by Na+ was 119 mM. External Li+ also blocked Ba2+ currents in a concentration-dependent manner, with an IC50 of 97 mM. Na+ block of Ba2+ currents was dependent on [Ba2+]; increasing [Ba2+] progressively reduced block with an IC50 of 2 mM. External Na+ had no effect on voltage-dependent activation or inactivation of the channel. These data suggest that at physiological concentrations, Na+ and Ca2+ compete for occupancy in a pore already occupied by a single Ca2+. Occupancy of the pore by Na+ reduced Ca2+ channel conductance, such that in physiological solutions, Ca2+ channel currents are between 50 and 70% of maximal. 相似文献