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771.
772.
Cristina Peggion Claudia Piazza Fernando Formaggio Marco Crisma Claudio Toniolo Bernard Kaptein Quirinus B. Broxterman Johan Kamphuis 《Letters in Peptide Science》2000,7(1):9-16
We synthesized by solution-phase methods thenaturally occurring, 10-amino acid residuelipopeptaibol antibiotics trikoningins KBI and KBII,and the [L-Iva1] KB analogue, in which the aminoacid in position 1 is different, with the aim atinvestigating the effect of hydrophobicity andchirality in that position. A solution conformationalanalysis, using FT–IR absorption and CD techniques,indicated that all of the three decapeptides arepredominantly helical in a membrane-mimeticenvironment. Permeability measurements showed anincrease of the activity from the [Aib1] peptideto the more hydrophobic [Iva1] peptides.Conversely, the effect of a change in chirality,obtained by replacing D-Iva1 with L-Iva, turnedout to be of minor significance. 相似文献
773.
Type I chaperonins: not all are created equal 总被引:8,自引:0,他引:8
Type I chaperonins play an essential role in the folding of newly translated and stress-denatured proteins in eubacteria, mitochondria and chloroplasts. Since their discovery, the bacterial chaperonins have provided an excellent model system for investigating the mechanism by which chaperonins mediate protein folding. Due to the high conservation of the primary sequence among Type I chaperonins, it is generally accepted that organellar chaperonins function similar to the bacterial ones. However, recent studies indicate that the chloroplast and mitochondrial chaperonins possess unique structural and functional properties that distinguish them from their bacterial homologs. This review focuses on the unique properties of organellar chaperonins. 相似文献
774.
Radical C-glycosylation of glucosamine derivatives by acrylic acid esters gave the corresponding 3-(alpha-C-glucosyl)-propionate derivatives in moderate yields. One of them was used as a versatile synthon for GLA-60 derivatives. However, the biological activity of these compounds as LPS-antagonists was disappointing. 相似文献
775.
Ceramidated GLA-60 derivatives 11 and 11' were synthesized from 1 via glycosidation of ceramide derivative 12 as a glycosyl acceptor with GLA-60 derivative 5 as a glycosyl donor, and successive conversion. Compound 11' showed only weak LPS-antagonistic activity without showing any LPS-agonistic activity. 相似文献
776.
Kalabay L Fekete B Czirják L Horváth L Daha MR Veres A Fónyad G Horváth A Viczián A Singh M Hoffer I Füst G Romics L Prohászka Z 《Helicobacter》2002,7(4):250-256
Background. To investigate whether the Helicobacter pylori status influences levels of antibodies against mycobacterial heat shock protein (hsp) 65 and human hsp60 in systemic autoimmune diseases and to study the concentration of anti‐H. pylori antibodies in autoimmune patients and healthy controls. Materials and Methods. Antibodies against human heat‐shock protein hsp60, mycobacterial heat‐shock protein hsp65 were analyzed by ELISA. Anti‐Helicobacter antibodies were determined by enzyme immunoassay. Results. There was a markedly higher prevalence of H. pylori infection in undifferentiated connective tissue disease (82%) (n = 33) and systemic sclerosis (78%) (n = 55) but not in systemic lupus erythematosus (n = 49), polymyositis/dermatomyositis (n = 14), rheumatoid arthritis (n = 21) or primary Raynaud's syndrome (n = 26) compared with controls (59%) (n = 349). In autoimmune diseases H. pylori infection was associated with elevated levels of antihsp65 (p = .008) but not of antihsp60. Anti‐hsp65 levels were significantly higher in H. pylori‐infected (n = 129) than in uninfected patients (n = 69) (p = .0007). Conclusions. These findings indicate that in autoimmune diseases the infection with the H. pylori bacterium is associated with increased concentration of antimycobacterial hsp65. 相似文献
777.
We have examined the effect of polyoma virus infection of primary mouse embryo cells on the tyrosyl kinase activity associated with the cellular src gene product, pp60c-src. The results of our studies demonstrate that infection of mouse cells with wild-type polyoma virus or viral mutants capable of transforming rodent cells in culture and inducing tumors in animals results in the stimulation of pp60c-src tyrosyl kinase activity. The level of pp60c-src kinase stimulation in infected cells was found to be proportional to both the oncogenic potential of the virus strain used for infection and the characteristic phenotype of rodent cells transformed by the various strains of polyoma virus. Stimulation of pp60c-src kinase activity was not observed in mouse cells infected with transformation-defective strains of polyoma virus. In examining the kinetics of pp60c-src kinase stimulation in mouse cells at various times following wild-type polyoma virus infection, we found that the level of pp60c-src kinase activity correlated directly with the synthesis of polyoma virus-encoded tumor antigens. By comparing wild-type polyoma virus with other viral mutants in these experiments, we conclude that the stimulation of pp60c-src kinase activity in mouse cells following polyoma virus infection is associated with the synthesis of middle tumor antigen. 相似文献
778.
This paper gives current densities measured in homogeneous grounded human models exposed to vertical, 60-Hz electric fields. The methods used for these measurements were validated by measuring the current densities induced in a grounded hemisphere and in a grounded prolate hemispheroid; agreement between measurement and theory was good. For an unperturbed field strength of 10 kV/m, current densities measured in the human chest were in the range 125-300 nA/cm2. A strong horizontal current-density enhancement was observed in the axillae, with peak values of about 400 nA/cm2. The vertical current density in the arms, when held downward, was in the opposite direction to that in the chest. Current densities in the abdomen, pelvis, and legs were a strong function of whether the body was grounded through one or both feet. With one foot grounded, the horizontal current density in the lower pelvic region, just above the crotch, was 770 nA/cm2. This value was the largest of those measured in the head, arms, or torso of the human model. Scaling factors derived from these data and similar data for animals will provide a quantitative basis for comparing animal and human exposure to 60-Hz electric fields. In addition, current-density data given in this paper can be directly extrapolated to higher frequencies, at least to 1 MHz. These extrapolated data may be useful to individuals and groups involved in the determination of safety standards for the lower radiofrequency region. 相似文献
779.
When the capacity of leaves for orderly dissipation of excitation energy in photosynthesis is exceeded, one mechanism by which the excess energy appears to be dissipated is through a nonradiative decay process. This process is observed as a reversible quenching of chlorophyll fluorescence emission (77K) from both photosystem II and photosystem I which persists in darkness (Demmig and Björkman 1987, Planta 171, 171–184). Fluorescence quenching was induced in soybean (Glycine max (L.) Merr.) leaves by two methods: 1) changing the composition of the gas surrounding the leaf from normal air to 2% O2, 0% CO2 at a low, constant photon flux density (PFD=photon fluence rate), and 2) increasing the PFD in the presence of normal air. In either case the quenching was fully reversible after return to the original condition (low PFD, normal air). The half-time of the relaxation of the quenching was in the order of 30 min. Both treatments resulted in reversible dephosphorylation of the light-harvesting chlorophyll-protein complex of photosystem II (LHC-II). Treatment under photoinhibitory conditions (high PFD plus chloramphenicol) also caused dephosphorylation of LHC-II. Therefore, phosphorylation of LHC-II cannot account for the observed fluorescence quenching. In addition, our results indicate that in vivo a factor other than the redox state of the plastoquinone pool controls LHC-II phosphorylation. This factor may be 60/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">pH, the pH gradient across the thylakoid membranes.Abbreviations and symbols CAP
chloramphenicol
- Fo, FM, Fv
instantaneous, maximumr variable fluorescence emission
- LHC-II
light-haryesting chlorophyll-protein complex of PSII
- kDa
kilodalton
- 60/xxlarge916.gif" alt="Delta" align="BASELINE" BORDER="0">pH
pH gradient across the thylakoid membrane
- PFD
photon flux density (photon fluence rate)
- PQ
plastoquinone
- PSI, PSII
photosystem I, II
- Q
acceptor of PSII
C.I.W.-D.P.B. Publication No. 926 相似文献
780.
60-Hz electric-field effects on pineal melatonin rhythms: time course for onset and recovery 总被引:3,自引:0,他引:3
Rats exposed for 3 weeks to uniform 60-Hz electric fields of 39 kV/m (effective field strength) failed to show normal pineal gland circadian rhythms in serotonin N-acetyl transferase activity and melatonin concentrations. The time required for recovery of the melatonin rhythm after cessation of field exposure was determined to be less than 3 days. The rapid recovery suggests that the overall metabolic competence of the pineal is not permanently compromised by electric-field exposure, and that the circadian rhythm effect may be neuronally mediated. 相似文献