全文获取类型
收费全文 | 295篇 |
免费 | 17篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1961年 | 1篇 |
1960年 | 5篇 |
排序方式: 共有312条查询结果,搜索用时 15 毫秒
1.
Raman spectroscopy of cytoplasmic muscle fiber proteins. Orientational order. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Biophysical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The polarized Raman spectra of glycerinated and intact single muscle fibers of the giant barnacle were obtained. These spectra show that the conformation-sensitive amide I, amide III, and C-C stretching vibrations give Raman bands that are stronger when the electric field of both the incident and scattered radiation is parallel to the fiber axis (Izz). The detailed analysis of the amide I band by curve fitting shows that approximately 50% of the alpha-helical segments of the contractile proteins are oriented along the fiber axis, which is in good agreement with the conformation and composition of muscle fiber proteins. Difference Raman spectroscopy was also used to highlight the Raman bands attributed to the oriented segments of the alpha-helical proteins. The difference spectrum, which is very similar to the spectrum of tropomyosin, displays amide I and amide III bands at 1,645 and 1,310 cm-1, respectively, the bandwidth of the amide I line being characteristic of a highly alpha-helical biopolymer with a small dispersion of dihedral angles. A small dichroic effect was also observed for the band due to the CH2 bending mode at 1,450 cm-1 and on the 1,340 cm-1 band. In the C-C stretching mode region, two bands were detected at 902 and 938 cm-1 and are both assigned to the alpha-helical conformation. 相似文献
2.
Early mouse embryos produce and release factors with transforming growth factor activity 总被引:2,自引:0,他引:2
Angie Rizzino 《In vitro cellular & developmental biology. Plant》1985,21(9):531-536
Summary Previous studies have shown that extracts from mouse embryos at mid and late stages of development contain factors that exhibit
transforming growth factor activity. The work reported here demonstrates that cultured mouse embryos at significantly earlier
stages of development produce and release factors that exhibit the characteristic property of transforming growth factors.
Specifically, the data demonstrate that embryos cultured from the blastocyst stage in serum-containing medium or in serum-free
medium release factors that promote the anchorage-independent growth of normal rat kidney fibroblasts. It is shown that these
factors are produced and released by cells derived from the inner cell mass and by trophoblasts. The precise developmental
stage when production of these factors first begins has not been determined but our findings suggest that these factors are
produced by cell types associated with early postimplatation embryos.
This work was supported by the Laboratory of Viral Carcinogenesis at the National Cancer Institute and by grants from the
National Cancer Institute (CA-36727) and the University of Nebraska Medical Center (22-271-732).
Editor's Statement This paper presents evidence that, in an in vitro assay system, early embryonic cells are capable of both
synthesizing and secreting TGF-like growth factors, implicating the production of these factors in the events of early development.
David W. Barnes 相似文献
3.
D Pigeon R Drissi-Daoudi F Gros J Thibault 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1986,302(12):435-438
Rat pheochromocytoma contains a protein kinase activity which remains associated with tyrosine hydroxylase (TH) during its purification. The incorporation of phosphate in TH is observed after incubation of TH with labelled ATP and magnesium without the need for an exogenous protein kinase. This Ca2+ and cAMP-independent kinase activity is different from previously described TH phosphorylating kinases from rat pheochromocytoma and other tissues. 相似文献
4.
5.
Angie Rizzino Peter Kazakoff John Nebelsick 《In vitro cellular & developmental biology. Plant》1990,26(5):537-542
Summary Previous studies have shown that cell density can regulate the binding of several growth factors. To determine whether cell
density exerts a uniform effect on the expression of epidermal growth factor (EGF) receptors, seven cell lines were examined
in detail. For each cell line, EGF binding was found to decrease as cell density increases. Scatchard analysis of the binding
data reveals that decreases in EGF binding are due to reductions in the number of cell surface EGF receptors. The only apparent
exception is the effect of cell density on the binding of EGF to A-431 cells. For these cells, increases in cell density lead
to two effects: decreases in the number of high affinity EGF receptors and increases in the total number of EGF receptors.
In addition to the effects of cell density on EGF receptors, it was determined that increases in cell density can coordinately
down-regulate receptors for as many as four different growth factors. Overall, the findings described in this report for EGF
and those previously described for transforming growth factor type-β (TGF-β) and fibroblast growth factor (FGF) demonstrate
the existence of a common mechanism for down-regulating growth factor receptors.
This work was supported by grants from the Nebraska Department of Health (89-51), the National Cancer Institute (Laboratory
Research Center Support Grant, CA36727), and the American Cancer Society (Core Grant ACS SIG-16).
EDITOR'S STATEMENT The paper by Rizzino et al. demonstrates that receptor number decreases as a function of cell density.
This may represent a mechanism by which cell proliferation is reduced as cell density increases. 相似文献
6.
7.
The 17 kb kps gene cluster of Escherichia coli K1, which encodes the information required for synthesis, assembly and translocation of the polysialic acid capsule of E. coli K1, is divided into three functional regions. Region 3 contains two genes, kpsM and kpsT, essential for the transport of capsule polymer across the cytoplasmic membrane. The hydrophobicity profile of KpsM suggests that it is an integral membrane protein while KpsT contains a consensus ATP-binding site. KpsM and KpsT belong to the ATP-binding cassette (ABC) superfamily of membrane transporters. In this study, we investigate the topology of KpsM within the cytoplasmic membrane using β-lactamase fusions and alkaline phosphatase sandwich fusions. Our analysis provides evidence for a model of KpsM having six membrane-spanning regions, with the N- and C-terminal domains facing the cytoplasm, and a short domain within the third periplasmic loop, which we refer to as the SV–SVI linker localizing in the membrane. Protease digestion studies are consistent with regions of KpsM exposed to the periplasmic space. In vivo cross-linking studies provide support for dimerization of KpsM within the cytoplasmic membrane. Linker-insertion and site-directed mutagenesis define the N-terminus, the first cytoplasmic loop, and the SV-SVI linker as regions that are important for the function of KpsM in K1 polymer transport. 相似文献
8.
9.
Angie Rizzino Alan B. Blumenthal 《In vitro cellular & developmental biology. Plant》1978,14(5):437-442
Summary We synchronized Drosophila cell lines (Schneider's line 2 and Kc) by allowing the cells to enter the stationary phase of growth and then diluting them into fresh culture medium. The cells
of both cell lines entered S phase, after an 8- to 14-hr delay, in a state of partial synchrony; 60 to 80% of the cell population
accumulated in S phase. Measurements of the cell cycle phases of Schneider's line 2 cells (S=14 to 16 hr; G2=6 to 8 hr; M=0.4 hr) were similar to those of Kc cells.
This work was performed under the auspices of the U.S. Energy Research and Development Administration. A.R. was supported
by an NIH post-doctoral fellowship, No. CA01060. 相似文献
10.
Y Cherifi C Pigeon M Le Romancer A Bado F Reyl-Desmars M J Lewin 《The Journal of biological chemistry》1992,267(35):25315-25320
The histamine H3 receptor agonist (R)alpha-methylhistamine (MeHA) inhibited, in a nanomolar range, basal and carbachol-stimulated inositol phosphate formation in the human gastric tumoral cell line HGT1-clone 6. The inhibition was reversed by micromolar concentrations of the histamine H3 receptor antagonist thioperamide and was sensitive to cholera or pertussis toxin treatment. Using [3H]N alpha-MeHA as specific tracer, high affinity binding sites were demonstrated with a Bmax of 54 +/- 3 fmol/mg of protein and a KD of either 0.61 +/- 0.04 or 2.2 +/- 0.4 nM, in the absence or presence of 50 microM GTP[gamma]S, respectively. The binding sites were solubilized by Triton X-100 and prepurified by gel chromatography. They were separated from the histamine H2 receptor sites by filtration through Sepharose-famotidine and finally retained on Sepharose-thioperamide. The purified sites concentrated in one single silver-stained protein band of 70 kDa in SDS-polyacrylamide gel electrophoresis. They specifically bound [3H]N alpha-MeHA with a KD of 1.6 +/- 0.1 nM and a Bmax of 12,000 +/- 750 pmol/mg of protein. This corresponds to a 90,225-fold purification over cell lysate and a purity degree of 84%. Binding was competitively displaced by N alpha-MeHA (IC50 = 5.8 +/- 0.7 nM), (R) alpha-MeHA (IC50 = 9 +/- 1 nM), and thioperamide (IC50 = 85 +/- 10 nM), but not by famotidine (H2 antagonist) or by mepyramine (H1 antagonist). These findings provide the first evidence for solubilization, purification, and molecular mass characterization of the histamine H3 receptor protein and for the negative coupling of this receptor phosphatidylinositol turnover through a so far unidentified G protein. 相似文献