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1.
N
-(carboxymethyl)lysine, an advanced glycation end product, is present in the human lens. The effects of CML formation on protein conformation and stability were studied using the recombinant C-crystallin as a model. Conformational change was studied by spectroscopic measurements such as fluorescence and circular dichroism. Conformational stability was determined by unfolding with heat. The results indicated that no conformational change was observed due to CML formation, but conformational stability decreased. These observations can be explained in terms of the relatively stable structure of -crystallin, especially when compared with other crystallins. The lens nucleus is rich in -crystallin and its stable conformation can assist -crystallin sustained insults and remain soluble. 相似文献
2.
Natural abundance of 15N ( 15N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The 15N values of non-N2-fixing trees in Brazil were +4.5±1.9, which is lower than those of soil nitrogen (+8.0±2.2). In contrast, mimosa and kudzu had very low 15N values (–1.4+0.5). The 15N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The 15N values of non-N2-fixing trees in Thailand were +4.9±2.0. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low 15N values, close to the value of atmospheric N2 (0), pointing to a major contribution of N2 fixation in these plants. Cassia spp. and Tamarindus indica had high 15N values, which confirms that these species are non-nodulating legumes. The 15N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N2 fixation in these legumes. 相似文献
3.
Summary The perdeuteration of aliphatic sites in large proteins has been shown to greatly facilitate the process of sequential backbone and side-chain 13C assignments and has also been utilized in obtaining long-range NOE distance restraints for structure calculations. To obtain the maximum information from a 4D 15N/15N-separated NOESY, as many main-chain and side-chain 1HN/15N resonances as possible must be assigned. Traditionally, only backbone amide 1HN/15N resonances are assigned by correlation experiments, whereas slowly exchanging side-chain amide, amino, and guanidino protons are assigned by NOEs to side-chain aliphatic protons. In a perdeuterated protein, however, there is a minimal number of such protons. We have therefore developed several gradient-enhanced and sensitivity-enhanced pulse sequences, containing water-flipback pulses, to provide through-bond correlations of the aliphatic side-chain 1HN/15N resonances to side-chain 13C resonances with high sensitivity: NH2-filtered 2D 1H-15N HSQC (H2N-HSQC), 3D H2N(CO)C/ and 3D H2N(COC/)C/ for glutamine and asparagine side-chain amide groups; 2D refocused H(N/)C/ and H(N/C/)C/ for arginine side-chain amino groups and non-refocused versions for lysine side-chain amino groups; and 2D refocused H(N)C and nonrefocused H(N.)C for arginine side-chain guanidino groups. These pulse sequences have been applied to perdeuterated 13C-/15N-labeled human carbonic anhydrase II (2H-HCA II). Because more than 95% of all side-chain 13C resonances in 2H-HCA II have already been assigned with the C(CC)(CO)NH experiment, the assignment of the side-chain 1HN/15N resonances has been straightforward using the pulse sequences mentioned above. The importance of assigning these side-chain HN protons has been demonstrated by recent studies in which the calculation of protein global folds was simulated using only 1HN-1HN NOE restraints. In these studies, the inclusion of NOE restraints to side-chain HN protons significantly improved the quality of the global fold that could be determined for a perdeuterated protein [R.A. Venters et al. (1995) J. Am. Chem. Soc., 117, 9592–9593].To whom correspondence should be addressed. 相似文献
4.
Jean-Michel Wieruszeski Jean-Claude Michalski Jean Montreuil Gérard Strecker 《Glycoconjugate journal》1990,7(1):13-26
The major pentasaccharides Fuc(1-2)[GalNAc(1-3)]Gal(1-4)[Fuc(1-3)]Glc and Fuc(1-2) [Gal(1-3)]Gal(1-4)[Fuc(1-3)]Glc, which are normally present in the urine of bloodgroup A Leb and B Leb healthy subjects, were each found to be contaminated by a minor component when analysed by1H-NMR. The determination of these structures, Fuc(1-2) [GalNAc(1-3)]Gal(1-3)[Fuc(1-4)]Glc and Fuc(1-2) [Gal(1-3)]Gal(1-3)[Fuc(1-4)]Glc, was based on the results of methylation analysis and1H/13C-NMR spectroscopy.Abbreviations HPLC
high performance liquid chromatography
- GLC
gas liquid chromatography
- NMR
nuclear magnetic resonance
- COSY
correlation spectroscopy
- Gal
d-galactopyranose
- GalNAc
2-acetamido-2-deoxy-d-galactopyranose
- Glc
d-glucopyranose
- Fuc
l-fucopyranose
- LNDFH I
lacto-N-difucohexaose I (Leb determinant 相似文献
5.
Jan B L Damm Hans Voshol Karl Hård Johannis P Kamerling Gijs W K Van Dedem Johannes F G Vliegenthart 《Glycoconjugate journal》1988,5(3):221-233
TheN-linked carbohydrate chains of the-subunit of highly purified urinary human chorionic gonadotropin have been re-investigated. The oligosaccharides were released enzymatically by peptide-N
4-(N-acetyl--glucosaminyl)asparagine amidase-F, and fractionated by a combination of FPLC and HPLC. As a result of the application of improved fractionation methods, apart from the earlier reported carbohydrate chains, also small amounts of trisialo tri- and tri-antennary oligosaccharides were found. The primary structures of the latter carbohydrate chains have been determined by 500-MHz1H-NMR spectroscopy to beAbbreviations hCG
human chorionic gonadotropin
- hCG-
-subunit
- hCG-
-subunit
- PNGase-F
peptide-N
4-(N-acetyl--glucosaminyl)asparagine amidase-F (E.C. 3.5.1.52)
- endo-F
endo--N-acetylglucosaminidase-F (E.C. 3.2.1.96)
- SDS
sodium dodecyl sulphate
- PAGE
polyacrylamide gel electrophoresis
- CBB
coomassie brilliant blue R 250
- GlcNAc
N-acetylglucosamine
- NeuAc
N-acetylneuraminic acid
- Man
mannose
- Gal
galactose
- Fuc
fucose 相似文献
6.
J A Van Kuik R A Hoffmann J H G M Mutsaers H Van Halbeek J P Kamerling J F G Vliegenthart 《Glycoconjugate journal》1986,3(1):27-34
The 500-MHz1H-NMR characteristics of theN-linked carbohydrate chain Man1-6[Xyl1-2]Man1-4GlcNAc1-4[Fuc1-3]GlcNAc1-NAsn of the proteolytic enzyme bromelain (EC 3.4.22.4) from pineapple stem were determined for the oligosaccharide-alditol and the glycopeptide, obtained by hydrazinolysis and Pronase digestion, respectively. The1H-NMR structural-reporter-groups of the (1–3)-linked fucose residue form unique sets of data for the alditol as well as for the glycopeptide. 相似文献
7.
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
8.
Gerard Strecker Jean-Michel Wieruszeski Jean-Claude Michalski Jean Montreuil 《Glycoconjugate journal》1988,5(4):385-396
The structure of a new nonasaccharide isolated from human milk has been investigated. By using methylation analysis, FAB-MS and1H-and13C-NMR spectroscopy as basic methods of structural investigation, this oligosaccharide was identified as VI2--Fuc,V4-Fuc,III3--Fuc-p-lacto-n-hexaose: Fuc1-2Gal1-3[Fuc1-4]GlcNAc1-3Gal1-4[Fuc1-3]GlcNAc1-3Gal1-4Glc.Abbreviations COSY
correlation spectroscope
- DP
degree of polymerisation
- FAB-MS
fast atom bombardment-mass spectrometry
- HPLC
high performance liquid chromatography
- NMR
nuclear magnetic resonance
- GLC
gas-liquid chromatography 相似文献
9.
Katherine K. Richardson Renae M. Crosby Thomas R. Skopek 《Molecular & general genetics : MGG》1988,214(3):460-466
Summary DNA sequencing was used to determine the specific types of DNA base changes induced following in vivo exposure of Escherichia coli to the ethylating agent N-ethyl-N-nitro-N-nitrosoguanidine (ENNG) and the hydroxyethylating agent 1-(2-hydroxyethyl)-1-nitrosourea (HENU) using the xanthine guanine phosphoribosyltransferase (gpt) gene as the genetic target. We observed that 22/30 of the ENNG-induced mutations were GCAT transitions, 4/30 were ATGC transitions, 3/30 were ATTA transversions, and 1/30 was an ATCG transversion. We observed that 37/40 HENU-induced mutations were GCAT transitions and that the remaining 3/40 were ATGC transitions. A majority of the GCAT transitions induced by ENNG and HENU (68% and 73%, respectively) occurred at the second guanine of the sequence 5-GG(A or T)-3; this sequence specificity was similar to that previously seen with the alkylating agents N-methyl- and N-ethyl-N-nitrosourea (MNU and ENU) and N-methyl-N-nitro-N-nitrosoguanidine (MNNG). A DNA strand preference for the GA changes (antisense strand), previously noted for MNU, ENU, and MNNG, was observed following exposure to HENU and ENNG. The ATGC transitions induced by ENNG, HENU, and ENU also exhibit a sequence specificity with 13/13 mutations occurring at the T of the sequence 5-NTC-3. A strand preference was not apparent for these mutations. 相似文献
10.
Jan B L Damm Johannis P Kamerling Gijs W K van Dedem Johannes F G Vliegenthart 《Glycoconjugate journal》1987,4(2):129-144
For the structural analysis of the carbohydrate chains ofN-,O-glycoproteins a straightforward strategy was developed based on the cleavage of theN-linked chains with immobilized peptide-N
4-(N-acetyl--glucosaminyl) asparagine amidase-F (PN-Gase-F) fromFlavobacterium meningosepticum, followed by alkaline borohydride treatment of the remainingO-glycoprotein material. This methodology was applied to the isolation of the Asn- and Ser-linked carbohydrate chains of human chorionic gonadotrophin. The structures of the isolated oligosaccharides were verified by 500-MHz1H-NMR spectroscopy. The Asn-linked sugar chains were shown to be: NeuAc2-3Gal1-4GlcNAc1-2Man1-6[NeuAc2-3Gal1-4GlcNAc1-2Man1-3]Man 1-4GlcNAc1-4[Fuc1-6]0-1GlcNAc and Man1-6[NeuAc2-3Gal1-4GlcNAc1-2Man 1-3]Man1-4GlcNAc1-4GlcNAc. Also some minor constituents occurred. The structures of the Ser-linked oligosaccharides were established in the form of their oligosaccharide-alditols as: NeuAc2-3Gal1-3[NeuAc2-6]GalNAc, NeuAc2-3Gal 1-3GalNAc and NeuAc2-3Gal1-3[NeuAc2-3Gal1-4GlcNAc1-6]GalNAc.Abbreviations hCG
human chorionic gonadotrophin
- hCG-
-subunit
- hCG-
-subunit
- ElA
enzyme immunoassay
- PNGase-F
peptide-N
4-(N-acetyl--glucosaminyl)asparagine amidase-F (EC 3.5.1.52)
- SDS
sodium dodecyl sulphate
- GalNAc
N-acetylgalactosamine
- GlcNAc
N-acetylglucosamine
- NeuAc
N-acetylneuraminic acid
- Man
mannose
- Gal
galactose
- Fuc
fucose 相似文献
11.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
12.
Folkert Reck Matthias Springer Ernst Meinjohanns Hans Paulsen Inka Brockhausen Harry Schachter 《Glycoconjugate journal》1995,12(6):747-754
UDP-GlcNAc:Man1-3R 1-2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) catalyses the conversion of [Man1-6(Man1-3)Man1-6][Man1-3]Man-O-R to [Man1-6(Man1-3)Man1-6] [GlcNAc1-2Man1-3]Man-O-R (R=1-4GlcNAc1-4GlcNAc-Asn-X) and thereby controls the conversion of oligomannose to complex and hybrid asparagine-linked glycans (N-glycans). GlcNAc-T I also catalyses the conversion of Man1-6(Man1-3)Man-O-octyl to Man1-6(GlcNAc1-2Man1-3)Man-O-octyl. We have therefore tested a series of synthetic analogues of Man1-6(Man1-3)Man-O-octyl as substrates and inhibitors for rat liver GlcNAc-T I. The 2-deoxy and the 3-, 4- and 6-O-methyl derivatives are all good substrates confirming previous observations that the hydroxyl groups of the Man1-6 residue do not play major roles in the binding of substrate to enzyme. In contrast, all four hydroxyl groups on the Man1-3 residue are essential since the corresponding deoxy derivatives either do not bind (2- and 3-deoxy) or bind very poorly (4- and 6-deoxy) to the enzyme. The 2- and 3-O-methyl derivatives also do not bind to the enzyme. However, the 4-O-methyl derivative is a substrate (K
m
=2.6mm) and the 6-O-methyl compound is a competitive inhibitor (K
i=0.76mm). We have therefore synthesized various 4- and 6-O-alkyl derivatives, some with reactive groups attached to anO-pentyl spacer, and tested these compounds as reversible and irreversible inhibitors of GlcNAc-T I. The 6-O-(5-iodoacetamido-pentyl) compound is a specific time dependent inhibitor of the enzyme. Four other 6-O-alkyl compounds showed competitive inhibition while the remaining compounds showed little or no binding indicating that the electronic properties of the attachedO-pentyl groups influence binding.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
13.
Yoshiharu Matahira Atsushi Tashiro Toshinari Sato Hirokazu Kawagishi Taichi Usui 《Glycoconjugate journal》1995,12(5):664-671
N-acetylhexosaminidase fromNocardia orientalis catalysed the synthesis of lacto-N-triose II glycoside (-d-GlcNAc-(1-3)--d-Gal-(1-4)--d-Glc-OMe,3) with its isomers -d-GlcNAc-(1-6)--d-Gal-(1-4)--d-Glc-OMe (4) and -d-Gal-(1-4)-[-d-GlcNAc-(1-6)]--d-Glc-OMe (5) throughN-acetylglucosaminyl transfer fromN,N-diacetylchitobiose (GlcNAc2) to methyl -lactoside. The enzyme formed the mixture of trisac-charides3, 4 and5 in 17% overall yield based on GlcNAc2, in a ratio of 20:21:59. Withp-nitrophenyl -lactoside as an acceptor, the enzyme also producedp-nitrophenyl -lacto-N-trioside II (-d-GlcNAc-(1-3)--d-Gal-(1-4)--d-Glc-OC6H4NO2-p,6) with its isomers -d-GlcNAc-(1-6)--d-Gal-(1-4)--d-Glc-OC6H4NO2-p (7) and -d-Gal-(1-4)-[-d-GlcNAc-(1-6)]--d-Glc-OC6H4NO2-p (8). In this case, when an inclusion complex ofp-nitrophenyl lactoside acceptor with -cyclodextrin was used, the regioselectivity of glycosidase-catalysed formation of trisaccharide glycoside was substantially changed. It resulted not only in a significant increase of the overall yield of transfer products, but also in the proportion of the desired compound6.Abbreviations GlcNAc2
2-acetamido-2-deoxy--d-glucopyranosyl-(1-4)-2-acetamido-2-deoxy-d-glucose
- NAHase
N-acetylhexosaminidase
- -CD
-cyclodextrin 相似文献
14.
Rudolf Geyer Silvia Diabaté Hildegard Geyer Hans-Dieter Klenk Heiner Niemann Stephan Stirm 《Glycoconjugate journal》1987,4(1):17-32
Fowl plague virus, strain Dutch, was metabolically labeled withd-[2-3H]mannose, or withd-[6-3H]glucosamine, and the small subunit (HA2; 0.8 mg in total) of the viral hemagglutinin was isolated by preparative sodium dodecylsulfate-polyacrylamide gel electrophoresis. After proteolytic digestion, the radioactive oligosaccharides were sequentially liberated from the glycopeptides by treatment with different endo--N-acetylglucosaminidases and with peptide:N-glycosidase or, finally, by hydrazinolysis. In this manner, four groups of glycans could be obtained by consecutive gel filtrations and were subfractionated by HPLC. The structures of the individual oligosaccharides were analyzed by micromethylation, by acetolysis or by digestion with exoglycosidases. The major species amongst the high mannose glycans at Ans-406 of the viral glycopolypeptide were found to be Man1-2Man1-3(Man1-2Man1-6)Man1-6(Man1-2Man1-2Man1-3)Man1-4GlcNac1-4GlcNAc and Man1-3(Man1-2Man1-6)Man1-6(Man1-2Man1-2Man1-3)Man1-4GlcNAc1-4GlcNAc, while the complex glycans at Asn-478 are predominantly GlcNAc1-2Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc (lacking, in part, one of the outerN-acetylglucosamine residues) and GlcNAc1-2Man1-3(Gal1-4GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc.Abbreviation BSA
bovine serum albumin
- endo D (F,H)
endo--N-acetyl-d-glucosaminidase D (F,H)
- HA
hemagglutinin (HA1, large subunit of HA
- HA2
small subunit
- FPV
fowl plague virus
- PNGase F
peptide:N-glycosidase F
- SDS
sodium dodecylsulfate 相似文献
15.
P. A. Dibrov R. L. Lazarova V. P. Skulachev M. L. Verkhovskaya 《Journal of bioenergetics and biomembranes》1989,21(3):347-357
Addition of Na+ to the K+-loadedVibrio alginolyticus cells, creating a 250-fold Na+ gradient, is shown to induce a transient increase in the intracellular ATP concentration, which is abolished by the Na+/H+ antiporter, monensin. The pNa-supported ATP synthesis requires an additional driving force supplied by endogenous respiration or, alternatively, by a K+ gradient (high [K+] inside). In the former case, ATP formation is resistant to the protonophorous uncoupler. Dicyclohexylcarbodiimide and diethylstilbestrol, but not vanadate, completely inhibit Na+ pulse-induced ATP formation. The data agree with the assumption that Na+-ATP-synthase is involved in oxidative phosphorylation inV. alginolyticus. Interrelation of H+ and Na+ cycles in bacteria is discussed.Abbreviations
and
electrochemical gradients of H+ and Na+, respectively
-
transmembrane electric potential difference
- pH, pNa, and pK
concentration gradients of H+, Na+, and K+, respectively
- CCCP
carbonyl cyanidem-chlorophenylhydrazone
- DCCD
N,N-dicyclohexylcarbodiimide
- DES
diesthylstilbestrol
- HQNO
2-heptyl-4-hydroxyquinolineN-oxide
- Tricine
N[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine 相似文献
16.
Holger Stephan Stefan Freund Werner Beck Günther Jung Jean-Marie Meyer Günther Winkelmann 《Biometals》1993,6(2):93-100
Novel linear hydroxamate/hydroxycarboxylate siderophores from strains of Pseudomonas cepacia were isolated and named ornibactins. The ornibactins represent modified tetrapeptide siderophores, possessing the sequence l-Orn1(N
-OH, N
-acyl)-d-threo-Asp(-OH)-l-Ser-l-Orn4(N
-OH, N
-formyl)-1,4-diaminobutane. The N
-acyl groups of Orn1(N
-OH, N
-acyl) may vary and represent the three acids 3-hydroxybutanoic acid, 3-hydroxyhexanoic acid and 3-hydroxyoctanoic acid, leading to a mixture of three different ornibactins, designated according to their acyl chain length as ornibactin-C4, ornibactin-C6 and ornibactin-C8. Each of the siderophores is accompanied by a small amount of a more hydrophilic component with a 16 a.m.u. higher mass. The structure elucidation was based on results from gas chromatography amino acid analysis, electrospray mass spectrometry, and one- and two-dimensional nuclear magnetic resonance techniques. 相似文献
17.
G. P. Vlasov V. I. Korol'kov G. A. Pankova I. I. Tarasenko A. N. Baranov P. B. Glazkov A. V. Kiselev O. V. Ostapenko E. A. Lesina V. S. Baranov 《Russian Journal of Bioorganic Chemistry》2004,30(1):12-20
We attempted to find some compounds for the effective delivery of gene constructs into cells and obtained two trispherical dendrimers on the basis of lysine, (Lys)8-(,-Lys)4-(,-Lys)2-(,-Lys)-Ala-NH2 (D1) and ((Lys)8-(,-Lys)4-(,-Lys)2-,-Lys)-Ala-[Lys(Plm)]2-Ala-NH2 (D2), as well as the starburst polymeric derivatives of D1, (pVIm)
8
-D1 and (pLys)
n
-D1, containing poly(N-vinylimidazole) and polylysine chains single-point bound to the dendrimer amino groups. The conditions of dendrimer–plasmid DNA complex formation were studied. The intracellular localization of these complexes and the expression of gene constructs delivered with their help were analyzed in transfection experiments on the HeLa cell cultures of human epithelial carcinoma and on mouse C2C12 myoblasts. It was found that the chemical structure of dendrimer D1 and its derivatives significantly affected the structure and properties of complex. 相似文献
18.
I examined the ability of frozen-thawed Avena sativa L. coleoptile sections under applied load to extend in response to the calcium chelators ethyleneglycol-bis-(-aminoethylether)-N,N,N,N-tetraacetic acid (EGTA) and 2-[(20bis-[carboxymethyl] amino-5-methylphenoxy)methyl]-6-methoxy-8-bis [carboxymethyl]aminoquinoline (Quin II). Addition of 5 mM EGTA to weakly buffered (0.1 mM, pH 6.2) solutions of 2(N-morpholino) ethanesulfonic acid (Mes) initiated rapid extension and wall acidification. When the buffer strength was increased (e.g. from 20 to 100 mM Mes, pH 6.2) EGTA did not initiate extension nor did it cause wall acidification. At 5 mM Quin II failed to stimulate cell extension or wall acidification at all buffer molarities tested (0.1 to 100 mM Mes). Both chelators rapidly and effectively removed Ca2+ from Avena sections. These data indicate that Ca2+ chelation per se does not result in loosening of Avena cells walls. Rather, EGTA promotes wall extension indirectly via wall acidification.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethylether)-N,N,N,N-tetraacetic acid
- Quin II
2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)methyl]-6-methoxy-8-bis(carboxymethyl)aminoquinoline
- Mes
2(N-morpholino)ethanesulfonic acid 相似文献
19.
Dinitrogen-fixing legumes are frequently assumed to be less water-use efficient than plants utilizing soil mineral N, because of the high respiratory requirements for driving N2 fixation. However, since respiration is assumed not to discriminate against 13C, any differences in water-use efficiency exclusively due to respiration should not be apparent in carbon isotope discrimination () values. Our objective was to determine if the source of N (N2 fixation versus soil N) had any effect on of field-grown grain legumes grown at different elevations. Four legume species, Glycine max, Phaseolus lunatus, P. vulgaris, and Vigna unguiculata, were grown on five field sites spanning a 633 m elevational gradient on the island of Maui, Hawaii. The legumes were either inoculated with a mixture of three effective strains of rhizobia or fertilized weekly with urea at 100 kg N ha-1 in an attempt to completely suppress symbiotic N2-fixing activity. In 14 of 20 analyses of stover and 12 of 15 analyses of seed values were significantly higher (p=0.10) in the inoculated plants than the N-fertilized plants. Nitrogen concentrations were generally higher in the fertilized treatments than the inoculated treatments. The different values obtained depending on N-source may have implications in using as an indicator of water-use efficiency or yield potential of legumes. 相似文献
20.
Summary The tryptic peptides from the
A and
B chains of cat hemoglobins A and B have been isolated and the amino acid compositions determined. Differences between the two chains were found in two peptides,T-1 (GlySer) andT-14 (AsnSer and LysArg). The GlySer and LysArg substitutions are placed at-1 and-144 respectively from earlier work, and the third substitution, AsnSer at-139 is suggested from this work. In addition, the presence of a blocked amino terminus in
B has been confirmed. Tentative sequences constructed by homology with known-chain structures suggest the occurrence of substitutions at
1
1 contacts in
A and
B that may be functionally significant. There are at least 18 differences in amino acid composition between cat
A and dog-chains and 22 differences between cat
A and normal adult human-chains. 相似文献