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1.
Bimolecular oxygenation of tri-liganded R-state human hemoglobin (HbA) is described by bi-exponential kinetics with association rate constants k
= 27.2 ± 1.3 (M·sec)-1 and k
= 62.9 ± 1.6 (M·sec)-1. Both the observed processes have been assigned to the bimolecular oxygenation of - and -subunits of the native tetrameric protein by molecular oxygen. The quantum yields of photodissociation within the completely oxygenated R-state HbA are
= 0.0120 ± 0.0017 and
= 0.044 ± 0.005 for - and -subunits, respectively. The oxygenation reactions of isolated PCMB- and PCMB-hemoglobin chains are described by mono-exponential kinetics with the association rate constants k
= 44 ± 2 (M·sec)-1 and k
= 51 ± 1 (M·sec)-1, respectively. The quantum yields of photodissociation of isolated PCMB- and PCMB-chains (0.056 ± 0.006 and 0.065 ± 0.006, respectively) are greater than that observed for appropriate subunits within the R-state of oxygenated HbA. 相似文献
2.
The interaction of heme-free (o) and heme-containing (h) chains of human hemoglobin has been monitored in 0.1 M potassium phosphate buffer, pH 7 or 8, at [5°C. Soret zero and first-derivative spectra were consistent with a uniform association reaction. Stopped-flow investigations demonstrated association rates on the order of 107 M–1 s–1. This was 100-fold more rapid than the reported rate of combination of h and h proteins. This encounter-like rate of semi--hemoglobin (oh) formation was increased by raising the pH from 7 to 8. pH change is known to affect the spatial arrangement of AB—GH helical entities. Molecular graphic analysis of modeled o protein superimposed over native h protein revealed an apo Mb-like structure with well-defined AB—GH segments. Repositioning of these core helical segments, resulting in increased conformational freedom of the 11 interface, was apparently responsible for the enhanced association properties of the o protein. 相似文献
3.
Judith L. Flippen-Anderson Clifford George Jeffrey R. Deschamps P. Anantha Reddy Anita H. Lewin George A. Brine 《Letters in Peptide Science》1994,1(3):107-115
Summary The solid state structures of two synthetic opioid peptides have been determined by X-ray single crystal analysis. The first X-ray structure is that of N,N-diallyl-(O-t-butyl)-Tyr-Aib-Aib-Phe-Leu-OMe (RTI02), a protected derivative of the -receptor selective antagonist ICI 174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH. ICI 174,864 is one of a series of rationally designed Aib-substituted enkephalin analogs which have shown site-specific antagonist properties. The second compound, the tetrapeptide Tyr-Tic-Phe-Phe-OH (TIPP), is one of a family of linear peptides containing the conformationally restricted Tic residue (tetrahydroisoquinoline-3-carboxylic acid). TIPP exhibits high affinity, selectivity and antagonism for the -receptor. Crystals of both peptides were obtained by slow evaporation and found to be monoclinic in space group P21. Unit cell dimensions for RTI02 were: a=13.619(4) , b=12.467(3) , c=13.750(4) , =96.03(4)o and V=2322(1) 3. The asymmetric unit contained one molecule of RTI02 and one molecule of methanol, giving a calculated density of 1.156 g cm-3. Unit cell dimensions for TIPP were: a=8.879(5) , b=20.146(8) , c=12.710(6) , =107.89(2)o and V=2164(2) 3. The asymmetric unit contained one molecule of TIPP and three molecules of acetic acid, giving a calculated density of 1.251 g cm-3. The RTI02 backbone has a double -bend, stabilized by two intramolecular hydrogen bonds. The TIPP backbone is also folded, but with only a single bend, stabilized by one intramolecular hydrogen bond and several hydrogen bonds to solvent molecules. Both compounds contain aromatic rings in close vicinity (4–6 ). 相似文献
4.
Ossi Renkonen Leena Penttilä Anne Makkonen Ritva Niemelä Anne Leppänen Jari Helin Anja Vainio 《Glycoconjugate journal》1989,6(1):129-140
A novel linear tetrasaccharide, Gal1-4GlcNAc1-6Gal1-4GlcNAc, was isolated from partial acid hydrolysates of metabolically labeled poly-N-acetyllactosaminoglycans of murine teratocarcinoma cells. It was characterized by exo-glycosidase sequencing and by mild acid hydrolysis followed by identification of all partial cleavage products. The tetrasaccharide, and likewise labelled GlcNAc1-6Gal1-4GlcNAc, resisted the action of endo--galactosidase (EC 3.2.1.103) fromE. freundii at a concentration of 125 mU/ml, while the isomeric, radioactive teratocarcinoma saccharides Gal1-4GlcNAc1-3Gal1-4GlcNAc and GlcNAc1-3Gal1-4GlcNAc were cleaved in the expected manner.Abbreviations WGA
wheat germ agglutinin
- BSA
bovine serum albumin
- [3H]GlcNAc1-4-GlcNAc1-4GlcNAcOL
N,N,NN'-triacetylchitotriose reduced with NaB3H4 相似文献
5.
Sujay K. Singh Edward K. Wakeland Ivica Vučak Zoltan A. Nagy Jan Klein 《Immunogenetics》1981,14(3-4):273-281
The B10.STA62 strain carries the H-2
w27 haplotype derived from a wild mouse captured in the vicinity of Ann Arbor, Michigan. Products of two class II loci composing this haplotype, A
and A
, are serologically, biochemically (by tryptic peptide mapping), and functionally indistinguishable from products controlled by the A
b
and A
/b
genes of the B10.A(5R) strain. In contrast, the polypeptide chain controlled by the third class II locus, E
, is different from that controlled by the E
/b
gene. This E
/w27
chain lacks an antigenic determinant present on the Eb molecule and carries determinants lacking on the Eb molecule, the E
/b
and E
/w27
peptide maps differ in at least six peptides, and cytotoxic T cells specific for the E
b
chains do not react with B10.STA62 target cells. This great difference between the E
/b
and E
/w27
chains suggests that the corresponding genes have not been derived from one another by a direct mutational conversion; instead, H-2
w27 appears to be a recombinant haplotype derived by crossing-over between the A
A
duplex and the E
locus. This is the first recombinant discovered separating these class II loci. 相似文献
6.
Cellular origin and distribution of transforming growth factor-β1 in the normal rat myocardium 总被引:6,自引:0,他引:6
Dr. M. Eghbali 《Cell and tissue research》1989,256(3):553-558
Summary Transforming growth factor- (TGF-) is a biologically active polypeptide present in normal tissues as well as transformed cells. Two structurally related forms of this peptide are TGF-
1 and TGF-
2. Using freshly isolated cardiomyocytes and non-myocyte heart cells, and a [32P]-labelled cDNA probe to human TGF-
1, we demonstrated that mRNA for TGF-
1 could be detected only in the nonmyocyte fraction of heart cells. In the present study, the distribution of TGF-
1 in the heart was determined by immunofluorescence staining by use of a polyclonal antibody to porcine TGF-
1 in cryostat sections of rat heart. Immunofluorescence staining was intense around the blood vessels and radially diffuse in the surrounding myocardium. 相似文献
7.
Cornelis H. Hokke Jos G. M. van der Ven Johannis P. Kamerling Johannes F. G. Vliegenthart 《Glycoconjugate journal》1993,10(1):82-90
Incubation of synthetic Man\1-4GlcNAc-OMe, GalNAc1-4GlcNAc-OMe, Glc1-4GlcNAc-OMe, and GlcNAc1-4GlcNac-OMe with CMP-Neu5Ac and rat liver Gal1-4GlcNAc (2-6)-sialyltransferase resulted in the formation of Neu5Ac2-6Man1-4GlcNAc-OMe, Neu5Ac2-6GalNAc1-4GlcNAc-OMe, Neu5Ac2-6Glc1-4GlcNAc-OMe and Neu5Ac2-6GlcNAc1-4GlcNAc-OMe, respectively. Under conditions which led to quantitative conversion of Gal1-4GlcNAc-OEt into Neu5Ac2-6Gal1-4GlcNAc-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz1H-NMR spectroscopy.Abbreviations 2D
2-dimensional
- CMP
cytidine 5-monophosphate
- CMP-Neu5Ac
cytidine 5-monophospho--N-acetylneuraminic acid
- COSY
correlation spectroscopy
- DQF
double quantum filtered
- HOHAHA
homonuclear Hartmann-Hahn
- MLEV
composite pulse devised by M. Levitt
- Neu5Ac
N-acetylneuraminic acid
- Neu5Ac2en
2-deoxy-2,3-didehydro-N-acetylneuraminic acid 相似文献
8.
Enhancement of protein precipitate strength and density by low-frequency conditioning 总被引:1,自引:0,他引:1
Dr. N. J. Titchener-Hooker Dr. R. V. McIntosh 《Bioprocess and biosystems engineering》1992,8(1-2):91-97
The use of a continuous, low-frequency conditioning process to alter the structure of protein precipitate aggregates is examined. An increase in the density of aggregates is correlated with the levels of fluid acceleration and hence hydrodynamic stress to which the aggregates are exposed during conditioning. A combination of low-frequency conditioning followed by shear break-up (as in the feed zone to a high-speed disk-stack centrifuge) is shown to result in a precipitate suspension of increased particle size at the fine end of the distribution, and having a greater sedimentation velocity. The resistance of large aggregates to shear disruption is increased by low-frequency conditioning.List of Symbols
CR
conditioning ratio
-
CRS
conditioning ratio after shearing
-
d m
amplitude of displacement
-
D m
particle size
-
D
c m
critical size for centrifuge recovery
-
f s–1
frequency of vibration
-
G s–1
mean velocity gradient
-
Q m3/s
volumetric throughput
-
SR
shear ratio
-
t s
ageing time
Greek Symbols
s–1
mass-average shear rate
-
K
sedimentation shape factor
-
a kg/m3
aggregate density
-
f kg/m3
fluid density
-
s kg/m3
solids density
- kg/m3
aggregate-suspension density difference
-
Ns/m2
kinematic viscosity
-
amplitude of pulse ratio (ref. 23, 9)
-
s
mean residence time
-
s
solids volume fraction 相似文献
9.
Neutral glycosphingolipids were isolated from quail small intestine and their structures were analysed. They contained: Gal1-4GlcCer(LacCer), Gal1-4GalCer(Ga2Cer), Gal1-4Gal1-4GlcCer(Gb3Cer), GlcNAc1-3Gal1-4GlcCer(Le3Cer), GalNAc1-4Gal1-4GlcCer(Gg3Cer), GalNAc1-4[GalNAc1-3]Gal1-4GlcCer(LcGg4Cer), and GalNAc1-3GalNAc1-3Gal1-4Gal1-4GlcCer (Forssman glycolipid) as well as glucosylceramide, galactosylceramide (Nishimura Ket al. 1984)Biochim Biophys Acta
796:269–76) and the Lex glycolipid, III3 Fuc-nLc4Cer (Nishimura Ket al. (1989)J. Biochem (Tokyo)
101:1315–18). The molecular species compositions of these glycosphingolipids were examined using fast atom bombardment-mass spectrometry linked with reversed-phase high-performance liquid chromatography. By such analysis, we could classify the quail glycosphingolipids into at least three classes: glycolipids rich in species having four hydroxyl groups in the ceramides (GalCer, Gg3Cer, LcGg4Cer and Lex), those rich in the ceramides ofN-acyl trihydroxysphinganine with normal fatty acids (Lc3Cer), and glycolipids rich in the ceramides ofN-acyl sphingenine with normal fatty acids (LacCer, Gb3Cer and Forssman glycolipid). Immunohistochemical observation implies that the differences in the hydrophobic moieties specified the localization of glycosphingolipids in the tissue. 相似文献
10.
Folkert Reck Ernst Meinjohanns Matthias Springer Roland Wilkens Johannes A. L. M. Van Dorst Hans Paulsen Gabriele Möller Inka Brockhausen Harry Schachter 《Glycoconjugate journal》1994,11(3):210-216
UDP-GlcNAc: Man1-6R (1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complexN-glycans. We have tested a series of synthetic analogues of the substrate Man1-6(GlcNAc1-2Man1-3)Man-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attachesN-acetylglucosamine in 1-2 linkage to the 2-OH of the Man1-6 residue. The 2-deoxy analogue is a competitive inhibitor (K
i=0.13mm). The 2-O-methyl compound does not bind to the enzyme presumably due to steric hindrance. The 3-, 4- and 6-OH groups are not essential for binding or catalysis since the 3-, 4- and 6-deoxy and -O-methyl derivatives are all good substrates. Increasing the size of the substituent at the 3-position to pentyl and substituted pentyl groups causes competitive inhibition (K
i=1.0–2.5mm). We have taken advantage of this effect to synthesize two potentially irreversible GlcNAc-T II inhibitors containing a photolabile 3-O-(4,4-azo)pentyl group and a 3-O-(5-iodoacetamido)pentyl group respectively. The data indicate that none of the hydroxyls of the Man1-6 residue are essential for binding although the 2- and 3-OH face the catalytic site of the enzyme. The 4-OH group of the Man-O-octyl residue is not essential for binding or catalysis since the 4-deoxy derivative is a good substrate; the 4-O-methyl derivative does not bind. This contrasts with GlcNAc-T I which cannot bind to the 4-deoxy-Man- substrate analogue. The data are compatible with our previous observations that a bisectingN-acetylglucosamine at the 4-OH position prevents both GlcNAc-T I and GlcNAc-T II catalysis. However, in the case of GlcNAc-T II, the bisectingN-acetylglucosamine prevents binding due to steric hindrance rather than to removal of an essential OH group. The 3-OH of the Man1-3 is an essential group for GlcNAc-T II since the 3-deoxy derivative does not bind to the enzyme. The trisaccharide GlcNAc1-2Man1-3Man-O-octyl is a good inhibitor (K
i=0.9mm). The above data together with previous studies indicate that binding of the GlcNAc1-2Man1-3Man- arm of the branched substrate to the enzyme is essential for catalysis.
Abbreviations: GlcNAc-T I, UDP-GlcNAc:Man1-3R (1-2)-N-acetylglucosaminyltransferase I (EC 2.4.1.101); GlcNAc-T II, UDP-GlcNAc:Man1-6R (1-2)-N-acetylglucosaminyltransferase II (EC 2.4.1.143); MES, 2-(N-morpholino)ethane sulfonic acid monohydrate. 相似文献
11.
Claudia Zacharias Gerhild Van Echten-Deckert Elaine Wang Alfred H. Merrill Jr. Konrad Sandhoff 《Glycoconjugate journal》1996,13(2):167-175
Fumonisins, mycotoxins produced byFusarium moniliforme and a number of other fungi, are potent inhibitors of the sphinganine-N-acyltransferase, a key enzyme of sphingolipid biosynthesis, and cause neuronal degeneration, liver and renal toxicity, cancer and other injury to animals.In this study we investigated the effect of fumonisin B1 on the sphingolipids of developing chick embryos. After yolk sac injection of fumonisin B1 a concentration and time dependent increase of the sphinganine-over-sphingosine ratio of the embryos could be demonstrated. Studies were done to evaluate the effect of fumonisin B1 on the glycosphingolipid pattern of the chick embryos. In the presence of 72 µg fumonisin B1 per egg the incorporation of [14C]galactose and of [14C]serine into embryonic glycosphingolipids was reduced by about 70%, although the mass of glycosphingolipids was not affected by the toxin. However, a reduction of the wet weight of the treated embryos was observed. Additionally, histological examinations of whole embryo sections of control and fumonisin B1 treated embryos are presented. Fumonisin B1 caused haemorrhages under the skin as well as in the liver of treated embyros. A close correlation between disruption of sphingoid metabolism and light microscopic detectable tissue lesions could be observed.Abbreviations Cer
ceramide (N-acylsphingosine)
- FB1
fumonisin B1
- GM3
NeuAc23Gal14Glc11Cer
- GD3
NeuAc28NeuAc23Gal14Glc11Cer
- GD1a
NeuAc23Gal13GalNAc14(NeuAc23)Gal14Glc11Cer
- GT1b
NeuAc23Gal13GalNAc14(NeuAc28NeuAc23) Gal14Glc11Cer
- HPLC
high pressure liquid chromatography
- PBS
phosphate buffered saline
- PDMP
1-phenyl-2-dodecanoylamino-3-morpholino-1-propanol
- Sa
sphinganine
- So
sphingosine
- Sa/So
sphinganine-over-sphingosine
- TLC
thin layer chromatography
- Tris
Tris(hydroxymethyl)aminomethan
Dedicated to Dr Sen-itiroh Hakomori in celebration of his 65th birthday. 相似文献
12.
Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga 《Molecular and cellular biochemistry》1983,56(1):73-80
Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. 相似文献
13.
Lutz Birnbaumer Ning Qin Riccardo Olcese Erwin Tareilus Daniela Platano Jim Costantin Enrico Stefani 《Journal of bioenergetics and biomembranes》1998,30(4):357-375
Calcium channel subunits have profound effects on how 1 subunits perform. In this article we summarize our present knowledge of the primary structures of subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with 1 subunits, the effects of subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by subunits, such as long-lasting prepulse facilitation of 1C (absent in 1E) and inhibition by G protein dimer of 1E, absent in 1C. One subunit, a brain 2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of 1 in oocytes requires a subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for 1 alone channels seen in cells with limited subunit expression. In one model, dissociates from the mature 1 after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of would then have subunit composition 1. In the other model, the chaperoning remains associated with the mature channel and 1 alone channels would in fact be 1 channels. Upon co-expression of high levels of the regulated channels would have composition [1]. 相似文献
14.
Christopher J. Krco Donald L. Wassom Ellen J. Abramson Chella S. David 《Immunogenetics》1983,18(5):435-444
A method is described for the production of T-cell lines and clones specific for solubilized Trichinella spiralis antigens. hese T cells are antigen-specific and do not respond to challenge with a third party antigen (lysozyme). The proliferation responses of the cloned T cells are specifically inhibited by anti-I-E but not by anti I-A subregion monoclonal reagents. The inhibition patterns obtained are consistent with cis-gene complementation in B10.K cells involving the Ek
-chain and the Ek -chain of the I-E molecule. Inhibition is obtained with an Ek
-specific monoclonal antibody (H9-14.8) but not with an Ak
-specific monoclonal antibody (10-2.16). Inhibition was also observed with Ia.7-specific (H40-242) or Ia.22-specific (17-3-3) monoclonal antibodies. The inhibition patterns were confirmed by antigen presentation experiments using recombinant inbred mice. Only B 10.K (Ek
Ek
spleen cells and not B 10.A(5R) (Eb
Ek
) or B10.S(9R) (Es
Ek
) spleen cells could effectively present T. spiralis antigens. The role of hybrid Ia molecules in the immune response to T. spiralis is discussed. 相似文献
15.
-Glucuronidase from callus cultures of Scutellaria baicalensis Georgi was purified to apparent homogeneity by fractionated ammonium-sulfate precipitation and chromatography on diethylaminoethyl-cellulose, hydroxylapatite and baicalin-conjugated Sepharose 6B. A 650-fold purification was obtained by this purification system. When subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified protein migrated as a single band with a molecular mass of 55 kDa. We determined that the native enzyme has a molecular mass of 230 kDa using gel-filtration chromatography. These results suggested that the enzyme exists as a homotetramer composed of four identical 55-kDa subunits. The enzyme showed a broad pH optimum between 7.0 and 8.0. The K
m values were 9 M, 10 M, 30 M and 40 M for luteolin 3 -O--d-glucuronide, baicalin, wogonin 7-O--d-glucoronide and oroxlin 7-O--d-glucuronide, respectively. The enzyme was most active with flavone 7-O--d-glucuronides.Abbreviations BA
N6-benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- pI
isoelectric point
-
R
t
retention time 相似文献
16.
The conformational properties of the oligosaccharide chain of GM1 ganglioside containingN-glycolyl-neuraminic acid, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer, were studied through NMR nuclear Overhauser effect investigations on the monomeric ganglioside in dimethylsulfoxide, and on mixed micelles of ganglioside and dodecylphosphocholine in water. Several interresidual contacts for the trisaccharide core--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-were found to fix the relative orientitation of the three saccharides, while the glycosidic linkage of the terminal -Gal-was found to be quite mobile as the -Gal-(1-3)--GalNAc-disaccharide exists in different conformations. These results are similar to those found for two GM1 gangliosides containingN-acetyl-neuraminic acid and neuraminic acid [1].Abbreviations Ganglioside nomenclature is in accordance with Svennerholm [23] and the IUPAC-IUB Recommendations [24] GM3(Neu5Ac)
II3Neu5AcLacCer, -Neu5Ac-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer
- GM3(Neu5Gc)
II3Neu5GcLacCer, -Neu5Gc-(2-3)--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu5Ac)
II3Neu5AcGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu5Gc)
II3Neu5GcGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu5Gc-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GM1(Neu)
II3NeuGgOse4Cer, -Gal-(1-3)--GalNAc-(1-4)-[-Neu-(2-3)]--Glc-(1-1)-Cer
- GD1a
IV3Neu5AcII3Neu5AcGgOse4Cer, -Neu5Ac-(2-3)--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- GalNAc-GD1a
IV4GalNAcIV3Neu5AcII3Neu5AcGgOse4Cer, -GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-3)--GalNAc-(1-4)-[-Neu5Ac-(2-3)]--Gal-(1-4)--Glc-(1-1)-Cer
- Neu
neuraminic acid
- Neu5Ac
N-acetyl-neuraminic acid
- Neu5Gc
N-glycolyl-neuraminic acid
- Cer
ceramide 相似文献
17.
M. M. Ferguson 《Histochemistry and cell biology》1967,9(3):269-274
Summary Parotid, submandibular and sublingual glands were removed from rats and investigated histochemically. Pyruvate oxidase, iso-citric dehydrogenase, -ketoglutarate oxidase, succinic dehydrogenase, malate dehydrogenase and furfuryl alcohol dehydrogenase activity were observed in the salivary ducts which may be interpreted as significant of high metabolic activity.The 11 -hydroxysteroid dehydrogenase in these ducts displayed marked substrate specificity utilizing 11-hydroxyandrostenedione and cortisol but not 11 -hydroxyoestrone or 11 -hydroxyprogesterone. The relationship between corticosteroids and salivary electrolyte concentrations is discussed. 相似文献
18.
In this report we provide evidence for the expression of antigenic epitopes on mouse (2-microglobulinb 2m
b) that result from assembly with cognate H-2 class I heavy chains. For the cell line 69.9.15 (2ma × 2mb), which expresses a mutant cytosolic form of H-2Kb and wild-type H-2Db, flow cytometry with rabbit antiserum against mouse 2m displayed 2m expression by cells grown in the presence or absence of fetal calf serum. By contrast, the epitopes identified by the 2mb-specific monoclonal antibody (mAb) S19.8 and clone 23 were not expressed by 69.9.15 cells grown in serum-containing conditions, and although S19.8 reactivity was weakly recovered by culture in the absence of serum, no such reacitivity was observed with clone 23. Strong expression of these epitopes was achieved following transfection of 69.9.15 cells with the wild-type H-2K
b gene, indicating that the 2mb epitopes defined by mAb S19.8 and clone 23 were expressed when 2mb was assembled with an appropriate heavy chain. In support of this conclusion, we observed the recovery of the S19.8 and clone 23 epitopes by in vitro assembly of H-2Kb heavy chains with 2mb in the presence of the VSV N protein p52–59; however, such epitopes were expressed neither by 2mb prior to heterodimer assembly nor by non-conformed 2mb present in tissue culture supernatants recovered from H-2 class I surface positive cells. Taken together, these data indicate that in addition to the property of 2m to modify the antigenicity of the MHC class I heavy chains, 2m epitopes are induced in a reciprocal manner by assembly with MHC class I heavy chain molecules.
Correspondence to: R. A. Zeff. 相似文献
19.
K. Shimizu 《Biochemical genetics》1987,25(3-4):197-203
DNA polymorphism patterns linked to the A-globin gene were analyzed in healthy Japanese using four different restriction endonucleases. The chromosomes with the A-globin gene were mapped through an evaluation of the presence of seven different restriction sites (HincII 5 to ; HindIII in G and A; HincII in, and 3 to, 1; AvaII in ; Bam-HI 3 to ). Among 36 chromosomes analyzed, 20 chromosomes had a haplotype of [+–––––+]. Among 55 individuals examined, 7 possessed a homozygous haplotye of [+–––––+]. All Japanese with the AT-globin gene had a subhaplotype of [–++–+] 5 to the -globin gene. Their major haplotypes were [–++–+–+] and [–++–++–]. It was expected that the presence of the AT-globin gene in Japanese may be deduced from subhaplotypes 5 to the -globin gene. 相似文献
20.
Steryl glycosides are the predominant form of sterol at 88% of the total sterol in non-betalain producing calli of Beta vulgaris. The total sterol decreases and sterol form shifts from steryl glycosides to 97% free sterol upon the transition of non-betalain to betalain producing calli. A substantial decrease in stigmasterol (24--ethylcholesta-5,22E-dien-3-ol) and sitosterol (24-ethylcholest-5-en-3-ol) levels is observed during this transition, and alters the ratio of 7:5 sterols. Spinasterol (24- ethyl-5-cholesta-7,22E-dien-3-ol) is the dominant sterol at 43% and 95% of the total sterol in non-betalain producing and betalain producing calli. The level of 22-dihydrospinasterol (24-ethyl-5-cholest-7-en-3-ol) is reduced in both calli to 3% from 25% in leaves. Lanosterol (4,4,14-trimethyl-cholesta-8(9),24-dien-3-ol) and cycloartenol (9,19-cyclopropyl-4,4,14-trimethyl-cholest-24-en-3-ol) were identified in betalain and nonbetalain producing callus respectively. 相似文献