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1.
Summary
Bacillus thuringiensis var.kurstaki (HD-1)_was grown as a continuous phased culture in a cyclone fermentor. During the time course of the continuous phased cultivation (CPC), the culture was sampled to determine the efficiency of sporulation and parasporal crystal formation. Concurrently, plasmid DNA was extracted and resolved on agarose gels. The plasmid profile remained constant throughout 328 h of cultivation. However, during the same time period, asporogenous, acrystalliferous variants increased from<1% to>90% of the cells harvested. Our data suggests that the disappearance of parasporal crystals inB. thuringiensis var.kurstaki (HD-1) during CPC occurs independent of plasmid copy but may be due to defective sporulation. 相似文献
2.
Measurement of the light response of photosynthetic CO2 uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO2 uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A
net photosynthesis rate
-
D
1
rate of dissimilative respiration occurring in the light
-
f
loss factor
-
I
incident PPFD
-
I
effective absorbed PPFD
-
J
rate of whole electron transport
-
J
m
maximum rate of whole electron transport
-
p
c
intercellular CO2 partial pressure
- PPFD
photosynthetic photon flux density
-
q
effectivity factor for the use of light (electrons/quanta)
-
absorption coefficient
-
I
*
CO2 compensation point in the absence of dissimilative respiration (bar)
-
II
conversion factor for calculation of CO2 uptake from the rate of whole electron transport
-
convexity factor
Gas-exchange rates relate to the projective area and are given in mol·m-2·s-1. Electron-transport rates are given in mol electrons·m-2·s-1; PPFD is given in mol quanta·m-2·s-1. 相似文献
3.
Proton nmr parameters are reported for DMSO-d6 solutions of two receptor-selective substance P analogues: Ac[Arg6,Pro9]SP6-11, which is selective for the NK-1 (SP-P) receptor and [pGlu6,N-MePhe8]SP6-11, which selectively activates the NK-3 (SP-N) receptor. Full peak assignments of both analogues were obtained by COSY experiments. The chemical shifts, coupling constants, and temperature coefficients of amide proton chemical shifts as well as NOESY effects and calculated side-chain rotamer populations of Phe side chains are reported for both peptides. Analysis of coupling constants and temperature coefficients together with the nuclear Overhauser enhancement spectroscopy effects suggest that Ac[Arg6,Pro9]SP6-11 has a trans configuration about the Phe8-Pro9 amide bond and the preferred conformation of this analogue has a type I beta-turn. The nmr data for [pGlu6,N-MePhe8]SP6-11 suggest that this peptide exists as a mixture of cis-trans isomers in which the cis isomer can preferably adopt a type VI beta-turn conformation, and the trans isomer can adopt a gamma-turn conformation. There are indications that the two last turns are stabilized by a hydrogen bond between the syn carboxamide proton and the pGlu ring carbonyl. 相似文献
4.
Light reduces the excitation efficiency in the nss mutant of the sheep blowfly Lucilia 总被引:2,自引:2,他引:0 下载免费PDF全文
S Barash E Suss D G Stavenga C T Rubinstein Z Selinger B Minke 《The Journal of general physiology》1988,92(3):307-330
The nss (no steady state) phototransduction mutant of the sheep blowfly Lucilia was studied electrophysiologically using intracellular recordings. The effects of the nss mutation on the receptor potential are manifested in the following features of the light response. (a) The responses to a flash or to dim lights are close to normal, but the receptor potential decays close to the baseline level during prolonged illumination after a critical level of light intensity is reached. (b) The decline of the response is accompanied by a large reduction in responsiveness to light that recovers within 20 s in the dark. (c) The full reduction in responsiveness to light is reached when approximately 13% of the photopigment molecules are converted from rhodopsin (R) to metarhodopsin (M). (d) A maximal net pigment conversion from R to M by blue light induces persistent inactivation in the dark, without an apparent voltage response. This inactivation could be abolished at any time by M-to-R conversion with orange light. The above features of the mutant indicate that the effect of the nss mutation on the light response of Lucilia is very similar to the effects of the transient receptor potential (trp) mutation on the photoreceptor potential of Drosophila. Noise analysis and voltage measurements indicate that the decay of the receptor potential is due to a severe reduction in the rate of occurrence of the elementary voltage responses (bumps). The bumps are only slightly modified in shape and amplitude during the decline of the response to light of medium intensity. There is also a large increase in response latency during intense background illumination. These results are consistent with the hypothesis that separate, independent mechanisms determine bump triggering and bump shape and amplitude. The nss mutation affects the triggering mechanism of the bump. 相似文献
5.
We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
相似文献
6.
CONCOMITANT SYNTHESIS OF MEMBRANE PROTEIN AND EXPORTABLE PROTEIN OF THE SECRETORY GRANULE IN RAT PAROTID GLAND 总被引:10,自引:9,他引:1 下载免费PDF全文
Abraham Amsterdam Michael Schramm Itzhak Ohad Yoram Salomon Zvi Selinger 《The Journal of cell biology》1971,50(1):187-200
After enzyme secretion the membrane of the secretory granule, which had been fused to the cell membrane, was resorbed into the cell. Experiments were therefore carried out to test whether formation of new secretory granules involves reutilization of the resorbed membrane or synthesis of a new membrane, de novo, from amino acids. Incorporation of amino acids-14C into proteins of various cell fractions was measured in vivo, 30, 120, and. 300 min after labeling. At all times the specific radioactivity of the secretory granule membrane was about equal to that of the granule's exportable content. At 120 and 300 min the specific radioactivity of the granule membrane and of the granule content was much higher than that of any other subcellular fraction. It is therefore concluded that the protein of the membrane is synthesized de novo concomitantly with the exportable protein. The proteins of the granule membrane could be distinguished from those of the granule content by gel electrophoresis. All major bands were labeled proportionately to their staining intensity. The amino acid composition of the secretory granule membrane was markedly different from that of the granule's content and also from that of the mitochondrial membrane. The granule membrane showed a high proline content, 30 moles/100 moles amino acids. The analyses show that the radioactivity of the granule membrane is indeed inherent in its proteins and is not due to contamination by other fractions. The possibility is considered that the exportable protein leaves the endoplasmic reticulum already enveloped by the newly synthesized membrane. 相似文献
7.
Calcium binding properties of sarcoplasmic reticulum membranes 总被引:2,自引:0,他引:2
8.
9.
Inositol lipid signaling relies on an InsP3-induced Ca2+ release from intracellular stores and on extracellular Ca2+ entry, which takes place when the Ca2+ stores become depleted of Ca2+. This interplay between Ca2+ release and Ca2+ entry has been termed capacitative Ca2+ entry and the inward current calcium release activated current (CRAC) to indicate gating of Ca2+ entry by Ca2+-store depletion. The signaling pathway and the gating mechanism of capacitative Ca2+ entry, however, are largely unknown and the molecular participants in this process have not been identified. In this article
we review genetic, molecular, and functional studies of wild-type and mutantDrosophila photoreceptors, suggesting that thetransient receptor potential mutant (trp) is the first putative capacitative Ca2+ entry mutant. Furthermore, several lines of evidence suggest that thetrp gene product TRP is a candidate subunit of the plasma membrane channel that is activated by Ca2+ store depletion. 相似文献
10.