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1.
Four glycosidases were analyzed in 10 mm apical segments prepared from growing roots (15 mm) of Zea mays L. The pH optima were found to be 5.8 for -glucosidase, 4.4 for -galactosidase, 6.4 for -glucosidase and 6.0 for -galactosidase. The -glucosidase showed 4-fold higher activity than the -galactosidase. The distribution of the -glucosidase activity was signifcantly different from that of the -galactosidase, -glucosidase and -galactosidase.Abbreviations -Glu
-glucosidase
- -Gal
-galactosidase
- -Glu
-glucosidase
- -Gal
-galactosidase 相似文献
2.
Minimal photosynthetic catalytic F1() core complexes, containing equimolar ratios of the and subunits, were isolated from membrane-bound spinach chloroplast CF1 and Rhodospirillum rubrum chromatophore RrF1. A CF1-33 hexamer and RrF1-11 dimer, which were purified from the respective F1() complexes, exhibit lower rates and different properties from their parent F1-ATPases. Most interesting is their complete resistance to inhibition by the general F1 inhibitor azide and the specific CF1 inhibitor tentoxin. These inhibitors were earlier reported to inhibit multisite, but not unisite, catalysis in all sensitive F1-ATPases and were therefore suggested to block catalytic site cooperativity. The absence of this typical property of all F1-ATPases in the 11 dimer is consistant with the view that the dimer contains only a single catalytic site. The 33 hexamer contains however all F1 catalytic sites. Therefore the observation that CF1-33 can bind tentoxin and is stimulated by it suggests that the F1 subunit, which is required for obtaining inhibition by tentoxin as well as azide, plays an important role in the cooperative interactions between the F1-catalytic sites.Abbreviations CF0F1
chloroplast F0F1
- CF1
chloroplast F1
- CF1
chloroplast F1 subunit
- CF1
chloroplast F1 subunit
- CF1()
a complex containing equal amounts of the CF1 and subunits
- MF1
mitochondrial F1
- RrF0F1
Rhodospirillum rubrum F0F1
- RrF1
R. rubrum F1
- RrF1
R. rubrum F1 subunit
- RrF1
R. rubrum F1 subunit
- RrF1()
a complex containing equal amounts of the RrF1 and subunits
- Rubisco
Ribulose-1,5-bisphosphate carboxylase
- TF1
thermophilic bacterium PS3 F1 相似文献
3.
Neurosteroids are endogenous Central Nervous System (CNS) compounds which act mainly by allosteric modulation of the GABAA receptor complex. The presence of a 3-hydroxyl group and a 5-hydrogen atom have been found to be essential structural requirements for biological activity in mammals. In the present work we report the enhancing activity on [3H]GABA binding to its receptor sites in chick optic lobe produced by progesterone metabolites 3-hydroxy,5-pregnan-20-one (3,5-P) and 3-hydroxy,5-pregnan-20-one (3,5-P). Both steroids were found able to enhance [3H]GABA binding along ontogeny, displaying a similar profile at early developmental stages, while in adulthood 3,5-P had greater potency (EC50 0.22 M) and enhancing effect (Emax: 122%). In adult synaptic membranes, the two compounds displayed a complex interaction with the GABAA receptor, disclosed by a Schild plot with slope below one and an incomplete displacement of 3,5-P by its 3,5 isomer. Such complexity could be related to the steroidogenic profile in avian CNS, with 5-reduced progesterone metabolites present since early development, while 3,5-P is found only in adulthood. Bearing in mind differences between avian and mammalian steroidogenic profiles and the relevance of 5-steroids in early avian development, we propose that 3,5-P, instead of the classical potent 3,5-steroids, may be the endogenous modulator of GABAergic activity in developing avian brain. 相似文献
4.
Summary Analysis of -thalassemia syndromes in several German families revealed DNA deletion as well as nondeletion forms as the molecular basis for the defects. Thus, the -thalassemia haplotype was identified as the (–)3.7 rightward deletion form, and the region of the putative recombination process generating such a deletion was further characterized. In addition three different ° haplotypes, (--)MED, (--)>26, and ()T, could be detected using -and -globin gene-specific probes. 相似文献
5.
The purified isopropylmalate synthase of Alcaligenes eutrophus H 16 reacted with the following -keto acids and acyl-coenzyme A derivatives (in the sequence of decreasing affinities): -ketoisovalerate, -keto-n-valerate, -ketobutyrate and pyruvate; acetyl-CoA, propionyl-CoA, butyryl-CoA. malonyl-CoA, valeryl-CoA, and crotonyl-CoA. -Ketoisocaproate, however, is a strong inhibitor of the enzyme. All reactions catalyzed by isopropylmalate synthase were inhibited to the same extent by the endproduct l-leucine. the substrate saturation curves of -ketoisovalerate or other -keto acids and of acetyl-coenzyme A or other acyl-CoA derivatives had intermediary plateau regions; the Hill coefficient alternated between n
H
-values higher and lower than 1.0, indicating changes from positive to negative and from negative to positive cooperativity for the substrates. The products, isopropylmalate and free coenzyme A, showed competitive inhibition patterns against both substrates (-ketoisovalerate and acetyl-CoA). Free coenzyme A (1 M) inactivated the enzyme irreversibly. The 3-phosphate of coenzyme A and the free carboxyl group of -ketoisovalerate were involved in optimal binding of these substrates, but 3-dephospho-acetyl-coenzyme A and the methylester of -ketoisovalerate were also converted by this enzyme. A CH3–CH2-grouping of the -keto acids seemed to be necessary for binding this substrate.Abbreviations Used CoA
Coenzyme A
- Tris
Tris(hydroxymethyl)aminomethane hydrochloride
- DTNB
5,5-dithiobis-(2-nitrobenzoic acid)
- IPM
-Isopropylmalate
- KIV
-Ketoisovalerate
Prepared from doctoral thesis of the University of Göttingen 1973 相似文献
6.
Calf lens A-crystallin isolated by reversed-phase HPLC demonstrates a slightly more hydrophobic profile than B-crystallin. Fluorescent probes in addition to bis-ANS, like cis-parinaric acid (PA) and pyrene, show higher quantum yields or Ham ratios when bound to A-crystallin than to B-crystallin at room temperature. Bis-ANS binding to both A- and B-crystallin decreases with increase in temperature. At room temperature, the chaperone-like activity of A-crystallin is lower than that of B-crystallin whereas at higher temperatures, A-crystallin shows significantly higher protection against aggregation of substrate proteins compared to B-crystallin. Therefore, calf lens A-crystallin is more hydrophobic than B-crystallin and chaperone-like activity of -crystallin subunits is not quantitatively related to their hydrophobicity. 相似文献
7.
Marco Candela Sean C. Barker Leslie R. Ballou 《Molecular and cellular biochemistry》1993,120(1):43-50
To examine the possible role of basic fibroblast growth factor (FGF) in regulating the effects of TNF, we tested the effect of FGF on TNF-mediated PGE2 production and TNF receptor expression in human fibroblasts. We found that, while FGF alone had no effect on PGE2 production, it enhanced the amount of PGE2 produced in response to TNF between 3 and 11-fold. FGF stimulated TNF-induced PGE2 production independent of potential TNF-mediated IL-1 production, as neither anti-IL-1 mAbs nor IL-1 receptor antagonist protein (IRAP) inhibited TNF induced-PGE2 production or the stimulatory effect of FGF. A one minute exposure of cells to FGF prior to removal was sufficient to significantly enhance TNF-induced PGE2 production; the maximal FGF effect was reached after a 6 h preincubation. We also found that FGF significantly enhanced TNF receptor expression. Untreated fibroblasts expressed 3,900 receptors/cell, while cells treated with FGF for 6h expressed 9,500 receptors/cell, a 2.4-fold increase in receptor number; there was no apparent change in affinity for TNF (Kd 3.8×10–11 M). The FGF-mediated increase in TNF receptor expression and TNF-mediated PGE2 production could be abolished by FGF mAbs, indicating a specific FGF effect. These results show that FGF increases TNF receptor expression and suggest that this may account, at least in part, for the ability of FGF to enhance TNF-mediated PGE2 production in human fibroblasts. 相似文献
8.
Cartesio Favalli Teresa Jezzi Antonio Mastino Cristina Rinaldi-Garaci Carlo Riccardi Enrico Garaci 《Cancer immunology, immunotherapy : CII》1985,20(3):189-192
Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin 1 cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin 1 (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin 1 was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin 1 and -IFN could be the result of effects on differentiation of the NK lineage at different levels. 相似文献
9.
Gabriele Möller Folkert Reck Hans Paulsen Kanwal J. Kaur Mohan Sarkar Harry Schachter Inka Brockhausen 《Glycoconjugate journal》1992,9(4):180-190
UDP-GlcNAc: Man3R 2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) is the key enzyme in the synthesis of complex and hybrid N-glycans. Rat liver GlcNAc-T I has been purified more than 25,000-fold (M
r 42,000). TheV
max for the pure enzyme with [Man6(Man3)Man6](Man3)Man4GlcNAc4GlcNAc-Asn as substrate was 4.6 µmol min–1 mg–1. Structural analysis of the enzyme product by proton nuclear magnetic resonance spectroscopy proved that the enzyme adds anN-acetylglucosamine (GlcNAc) residue in 1–2 linkage to the Man3Man-terminus of the substrate. Several derivatives of Man6(Man3)Man-R, a substrate for the enzyme, were synthesized and tested as substrates and inhibitors. An unsubstituted equatorial 4-hydroxyl and an axial 2-hydroxyl on the -linked mannose of Man6(Man3)Man-R are essential for GlcNAc-T I activity. Elimination of the 4-hydroxyl of the 3-linked mannose (Man) of the substrate increases theK
M 20-fold. Modifications on the 6-linked mannose or on the core structure affect mainly theK
M and to a lesser degree theV
max, e.g., substitutions of the Man6 residue at the 2-position by GlcNAc or at the 3- and 6-positions by mannose lower theK
M, whereas various other substitutions at the 3-position increase theK
M slightly. Man6(Man3)4-O-methyl-Man4GlcNAc was found to be a weak inhibitor of GlcNAc-T I.Abbreviations BSA
Bovine serum albumin
- Bn
benzyl
- Fuc, F
l-fucose
- Gal, G
d-galactose
- GalNAc, GA
N-acetyl-d-galactosamine
- Glc
d-glucose
- GlcNAc, Gn
N-acetyl-d-glucosamine
- HPLC
high performance liquid chromatography
- Man, M
d-mannose
- mco
8-methoxycarbonyl-octyl, (CH2)8 COOOCH3
- Me
methyl
- MES
2-(N-morpholino)ethanesulfonate
- NMR
nuclear magnetic resonance
- PMSF
phenylmethylsulfonylfluoride
- pnp
p-nitrophenyl
- SDS
sodium dodecyl sulfate
- T
transferase
- Tal
d-talose
- Xyl
d-xylose;
- {0, 2 + F}
Man6 (GlcNAc2Man3) Man4GlcNAc4 (Fuc6) GlcNAc
- {2, 2}
GlcNAc2Man6 (GlcNAc2Man3) Man4GlcNAc4GlcNAc; M5-glycopeptide, Man6 (Man3) Man6 (Man3) Man4 GlcNAc4GlcNAc-Asn
Enzymes: GlcNAc-transferase I, EC 2.4.1.101; GlcNAc-transferase II, EC 2.4.1.143; GlcNAc-transferase III, EC 2.4.1.144; GlcNAc-transferase IV, EC 2.4.1.145; GlcNAc-transferase V, UDP-GlcNAc: GlcNAc2 Man6-R (GlcNAc to Man) 6-GlcNAc-transferase; GlcNAc-transferase VI, UDP-GlcNAc: GlcNAc6(GlcNAc2) Man6-R (GlcNAc to Man) 4-GlcNAc-transferase; Core 1 3-Gal-transferase, EC 2.4.1.122; 4-Gal-transferase, EC 2.4.1.38; 3-Gal-transferase, UDP-Gal: GlcNAc-R 3-Gal-transferase; blood group i 3-GlcNAc-transferase, EC 2.4.1.149; blood group I 6-GlcNAc-transferase, UDP-GlcNAc: GlcNAc3Gal-R (GlcNAc to Gal) 6-GlcNAc-transferase. 相似文献
10.
Eric Mossel Fernando Formaggio Giovanni Valle Marco Crisma Claudio Toniolo Mitsunobu Doi Toshimasa Ishida Quirinus B. Broxterman Johan Kamphuis 《Letters in Peptide Science》1998,5(2-3):223-225
In order to obtain further information on the role played by phenyl ring position in the C-methylated -amino acid side chain on peptide preferred conformation, the crystal-state structural preferences of C-methyl, C-phenylglycine peptides have been determined by X-ray diffraction. This study shows that either the fully extended conformation or the -bend/310-helical structures are adopted by peptides characterized by this C-methylated, -branched, aromatic -amino acid. 相似文献
11.
GABAA-receptors, the major synaptic targets for the neutotransmitter GABA, are gated chloride channels. By their allosteric drug-induced modulation they serve as molecular control elements through which the levels of anxiety, vigilance, muscle tension and epileptiform activity can be regulated. Despite their functional prominence, the structural requirements of fully functional GABAA-receptors are still elusive. Expression of cDNAs coding for the 1- and 1-subunits of rat brain yielded GABA-gated chloride channels which were modulated by barbiturates but displayed only agonistic responses to ligands of the benzodiazepine receptor. GABAA-receptors with fully functional benzodiazepine receptor sites were formed when the 1- and 1-subunits were coexpressed with the 2-subunit of rat brain. These receptors, however, failed to show cooperativity of GABA in gating the channel. In order to determine the subunit repertoire available for receptor assembly in different neuronal populations in vivo, the sites of subunit gene expression were (1, 2, 3, 5, 6, 1, 2, 3, 2) mapped by in situ hybridization histochemistry in brain sections. The mRNAs of the 1-, 1- and 2-subunits were co-localized e.g. in mitral cells of olfactory bulb, pyramidal cells of hippocampus as well as granule cells of dentate gyrus and cerebellum. The lack of colocalization in various other brain areas points to an extensive receptor heterogeneity. The presence of multiple GABAA-receptors in brain may contribute to synaptic plasticity, differential responsiveness of neurons to GABA and to variations in drug profiles.Special issue dedicated to Dr. Erminio Costa 相似文献
12.
Jacques Raymond Brahim Mimouni Jean-Louis Azanza 《Plant Systematics and Evolution》1994,193(1-4):69-79
The seed storage globulins from sixHelianthus and four hybrids were studied using mono and bidimensional gel SDS electrophoresis (+ 2 mercaptoethanol). The polypeptide composition of each subunit was determined. Different pairs are specifically expressed according to the species studied. Three typical patterns were discriminated. All the studied species exhibit five subunits: two of them are expressed in all the species (11 and 22). The subunit corresponding to the 11 pair is present inH. petiolaris and in the three populations ofH. annuus studied. The 2b2 pair is common toH. annuus andH. argophyllus. H. petiolaris presents two specific 2a2 and 44 pairs andH. annuus a specific 33 pair. InH. argophyllus 11 33 or 44 are never observed but are replaced by 13 and 31 pairs. Some globulins, poorly represented, are of forms but present chains of higher molecular weights (in the range 54–56 kDa). Expressing variations in the banding patterns between these species by the use of a similarity index reveals complete identity between the three populations ofH. annuus. Identity between the twoH. petiolaris studied is also observed.H. annuus andH. argophyllus appear to be closer to each other thanH. petiolaris concerning the seed storage globulins. 相似文献
13.
A. N. Luchnik 《Molecular biology reports》1980,6(1):3-9
A theory of conformational transitions in closed circular DNA as a function of topological linking number of the molecule () is elaborated taking into account topological and energetical considerations. The theory predicts a step-like dependence of a number of superhelical turns in DNA molecules () on . Thus, the number of superhelical turns = for small values of . For a large (when conformational transitions begin to occur) =–ij, where ij is the total angle of conformational transitions for a given . This prediction is in good agreement with published data on the dependence of the sedimentation coefficient of circular DNA molecules on their topological linking number. The results also allow to explain the disagreement between a number of titratable superhelical turns in circular DNA molecules and a number of supercoiles seen on electron micrographs for molecules with sufficiently large . 相似文献
14.
M. Ishimoto K. Suzuki M. Iwanaga F. Kikuchi K. Kitamura 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(3-4):425-429
Variation of seed -amylase inhibitors was investigated in 1 154 cultivated and 726 non-cultivated (wild and weedy) accessions of the common bean, Phaseolus vulgaris L. Four -amylase inhibitor types were recognized based on the inhibtion by seed extracts of the activities of porcine pancreatic -amylase and larval -amylase and larval -amylase of the Mexican bean weevil, Zabrotes subfasciatus Boheman. Of the 1 880 accessions examined most (1 734) were able to inhibit porcine pancreatic -amylase activity, but were inactive against the Z. subfasciatus larval -amylase; 41 inhibited only the larval -amylase activity, 52 inhibited the activities of the two -amylases, and 53 did not inhibit the activity of either of the -amylases. The four different inhibitor types were designated as AI-1, AI2, AI-3, and AI-0, respectively. These four inhibitor types were identified by the banding patterns of seed glycoproteins in the range of 14–20 kDa by using SDSpolyacrylamide gel electrophoresis. Additionally, four different banding patterns were recognized in accessions with AI-1, and were designated as AI-1a, 1b, 1c, and 1d. Two different patterns of the accessions lacking an -amylase inhibitory activity were identified and designated as AI-0a and AI-0b. The largest diversity for seed -amylase inhibitors was observed in non-cultivated accessions collected from Mexico where all eight inhibitor types were detected. The possible relationships between the variation of seed -amylase inhibitors and bruchid resistance are discussed. 相似文献
15.
Asish Ray Chaudhuri Isao Tomita Fukutaro Mizuhashi Kyoji Murata Richard F. Ludueña 《Journal of Protein Chemistry》1998,17(4):303-309
IKP104, a novel antimitotic drug, has two classes of binding sites on bovine brain tubulin with different affinities. IKP104, by itself, enhances the decay of tubulin, but in the presence of colchicine or podophyllotoxin, it stabilizes tubulin instead of opening up the hydrophobic areas [Luduena et al. (1995), Biochemistry
34, 15751–15759], Here, we have dissected these two apparently contradictory effects of IKP104 by cleaving the C-terminal ends of both and subunits of tubulin with subtilisin. We have found that the selective removal of the C-terminal ends from both the and subunits of tubulin lowers the sulfhydryl titer by approximately 1.5 mol/mol of dimer. Interestingly, IKP104 does not increase either the sulfhydryl liter or the exposure of hydrophobic areas of this subtilisin-treated tubulin (ss). Moreover, IKP104 lowers the sulfhydryl titer of ss tubulin approximately by 1 mol/mol and appears to inhibit completely the time-dependent decay of ss tubulin. The cleavage at the C-terminal ends of both and modulates the effect of IKP104 on the subunit, but not on the subunit. Fluorometric binding data analysis suggests that IKP104 binds to the ss tubulin only at the high-affinity site; the low-affinity site(s) disappear almost completely. The sulfhydryl titer data for and and the fluoromelric data therefore suggest that the interaction of IKP104 at the high-affinity site on tubulin is not regulated by the C-terminal domains of and and the effect of the high-affinity site is restricted largely to the subunit, while the low-affinity-site binding is modulated by the C-terminal domain of . It also appears that the stabilization and the acceleration of the decay of tubulin are mediated by distinct interactions of IKP104 with its high- and low-affinity sites on tubulin, respectively. 相似文献
16.
A. Kanamori K. Kitajima Y. Inoue S. Inoue Z. Xulei C. Zuber J. Roth J. Ye F. A. Troy II 《Histochemistry and cell biology》1994,101(5):333-340
Two particular types of sialoglycoproteins have been detected in fish: polysialoglycoproteins containing 28-linked polysialic acid (8Neu5Gc2)
n
present in unfertilized Salmonidae fish eggs, and glycoproteins bearing oligo/polymers of deaminated neuraminic acids (KDN) found in the vitelline envelope of the eggs and ovarian fluid. We report the preparation and characterization of a monoclonal antibody specifically recognizing oligo/polymers of KDN sequences in glycoproteins and its application in immunohistochemistry. Fusion of spleen cells from a BALB/c mouse immunized with a KDN-rich glycoprotein (KDN-gp) containing (8KDN2)
n
6(KDN23Gal13GlNAc13) GalNAc1 residues, with mouse myeloma cells yielded a hybrid cell line producing a monoclonal antibody that bound to KDN-gp, but not to KDN-gp depleted of KDN residues. The specificity of the monoclonal antibody, designated mAb.kdn8kdn, was determined by an enzyme-linked immunosorbent assay using KDN-gp samples that varied in KDN content. These antigens were prepared by the selective removal of KDN residues from the native KDN-gp. The mAb.kdn8kdn reacted most strongly with the intact KDN-gp and less strongly with KDN-gp samples containing decreased numbers of KDN residues. The mAb.kdn8kdn was shown specifically to recognize the 28-linked oligo/polyKDN sequences, (8KDN2)
n
, and to be able to distinguish specifically (8KDN2)
n
chains from (8Neu5Ac2)
n
and (8Neu5Gc2)
n
chains. The antibody was used successfully for the immunohistochemical detection of reactive KDN epitopes in sections of paraffin embedded rat pancreas. Several controls verified the specificity of the immunohistochemical staining, thus providing the first demonstration of (8KDN2)
n
sequences in a mammalian tissue. The mAb.kdn8kdn can now be used to search further for glycoconjugates containing (8KDN2)
n
chains and will facilitate studies on their biosynthesis, intracellular localization and function. 相似文献
17.
Summary -Tocopherol was identified in lipid extracts of bovine retinal outer segment (ROS) preparations. Positive identification was obtained by the thin layer chromatographic characteristics of the tocopherol form and its oxidation product -tocopherylquinone, and by the ultraviolet spectrum of the oxidized and KBH4-reduced form of the tocopherylquinone. In the ROS preparations used, -tocopherol chromanol was the predominant species, the quinone form accounting for 25% or less of the total. The concentration of -tocopherol in the ROS preparations was about 0.1 mole -tocopherol per mole rhodopsin, or about 1 nmole/mg, protein. Mitochondria from bovine retina contained about 0.4 nmole -tocopherol per mg protein. 相似文献
18.
Slezak Jan Schulze Wolfgang Stefankova Zuzana Okruhlicova Ludmila Danihel Ludovit Wallukat Gerd 《Molecular and cellular biochemistry》1996,159(1):39-45
By indirect immunofluorescence and preembedding peroxidase-diaminobenzidine technique the localization of polyclonal and monoclonal antibodies against 1, 2 and 3 isoforms of the Na,K-ATPase were studied in rat myocardium.The 1-subunit was identified predominantly on sarcolemma of cultured myocytes, neonatal, as well as adult cardiocytes. The 2 signal was localized around nuclei of cultured cardiocytes, very weak signals were seen in neonatal and more intense signal, were dispersed throughout the adult myocytes. The 3-subunit immunoreactivity was weak and localized in cell processes connecting individual cultured cells, on sarcolemma and intercalated discs of neonatal cells and very weak in adult working myocytes. Cytochemically demonstrated ouabain resistant Na,K-ATPase localized in junctional sarcoplasmic reticulum may represent 1 isoenzyme which is directly involved in modulation of action potential fluxes. 相似文献
19.
Spin-State-Selective Excitation (S3E), which forexample selectively excites amide proton resonances corresponding toexclusively either the or the spin state of the covalentlybound 15N atom is employed for E.COSY-type extraction ofheteronuclear J coupling constants. Instead of having one spectrum with twopeaks (corresponding to the or spin state of15N), S3E generates two spectra, each with onlyone peak for each 15N nucleus. These two spectra are generatedfrom the same data set, so that there is no reduction in sensitivitycompared to conventional 1JNH-resolved methods.Another interesting feature in comparison with conventional methods is that1JNH can be suppressed during the evolutionperiod, meaning that no heteronuclear multiplet structure is visible in the1 frequency dimension. The S3E pulsesequence element is combined with NOESY for measurement of3JN-H and JN-Hcoupling constants in either a hetero- or a homonuclear correlated version.Experimental confirmation is obtained using the protein RAP 17-;97(N-terminal domain of 2-macroglobulin ReceptorAssociated Protein). 相似文献
20.
The major barrier for xenotransplantation in humans is the presence of (1–3) Galactosyl epitopes (Gal) in xenogeneic tissue and the vast quantities of natural antibodies (Ab) produced by humans against this epitope. The binding of anti-Gal Ab to cells expressing Gal triggers a complement-mediated hyperacute rejection of target cells. The hyperacute rejection of whole cancer cells, modified to express Gal epitopes, could be exploited as a new cancer vaccine to treat human cancers. We tested this hypothesis in Galactosyltransferase knockout (GT KO) mice which, like humans, do not express Gal on their cell surfaces and can produce anti-Gal Ab. Forty-five percent of mice with preexisting anti-Gal Ab rejected Gal positive melanoma cells (B16Gal). These mice remained tumor-free for more than 90 days. The majority of control mice injected with B16Null, Gal negative cells succumbed to melanoma. The rejection of B16Gal induced strong long-lasting antitumor immunity against B16Null measured by the expansion of cytotoxic T lymphocytes. In addition, mice rejecting B16Gal were protected against melanoma since they survived a second rechallenge with B16Null. Protected mice developed antitumor immunity in the absence of autoimmune depigmentation (vitiligo). These results show that rejection of Gal positive melanoma cells can efficiently boost the immune response to other tumor associated antigens present in Gal negative melanoma cells. This study supports the concept of a novel anticancer vaccine to treat human malignancies. 相似文献