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1.
The magnitude of the proton motive force (p) and its constituents, the electrical () and chemical potential (-ZpH), were established for chemostat cultures of a protease-producing, relaxed (rel ) variant and a not protease-producing, stringent (rel +) variant of an industrial strain ofBacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of p with the specific growth rate was found. The calculated intracellular pH (pHin) was not constant but inversely related to . This change in pHin might be related to regulatory functions of metabolism but a regulatory role for pHin itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low and an increased value at higher . For both limitations, the ATP/ADP ratio was directly related to .The phosphorylation potential (G'p) was invariant with . From the values for G'p and p, a variable H+/ATP-stoichiometry was inferred: H+/ATP=1.83+0.52µ, so that at a given H+/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for =0 to max (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of G'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.Abbreviations CCCP carbonylcyanide-p-trichloromethoxyphenylhydrazone - DW dry weight of biomass - F Faraday's constant, 96.6 J/(mV × mol) - Fo chemostat outflow-rate (ml/h) - FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - G'p phosphorylation potential, the Gibbs energy change for ATP-synthesis from ADP and Pi - G'0p standard Gibbs energy change at specified conditions - H+/ATP number of protons translocated through - ATP synthase in synthesis of one ATP - H+/O protons translocated during transfer of 2 electrons from substrate to oxygen - specific growth rate (1/h) - H+ transmembrane electrochemical proton potential, J/mol - Mb molar weight (147.6 g/mol) of bacteria with general cell formula C6.0H10.8O3.0N1.2 - pHout,in extracellular, intracellular pH - Pi (intracellular) inorganic phosphate - p proton motive force, mV - pH transmembrane pH-difference - transmembrane electrical potential, mV - P/O number of ADP phosphorylated to ATP upon reduction of one O2– to H2O by two electrons transferred through the electron transfer chain - P/O (H+/O) × (H+/ATP)–1 - P/OF, P/ON P/O with the two electrons donated by resp. (NADH + H+) and FADH - q specific rate of consumption or production (mol/g DW × h) - rel +,rel stringent, relaxed genotype - R universal gas constant, 8.36 J/(mol × degree) - T absolute temperature - TPMP+ triphenylmethylphosphonium ion - TPP+ tetraphenyl phosphonium ion - Y growth yield, g DW/mol - Z conversion constant=61.8 mV for 310 K (37 °C) - ZpH transmembrane proton potential or chemical potential, mV  相似文献   

2.
Recently, we have developed an analytical, semi-microscopic theory for the macroscopic behavior of a solvent-containing black lipid film subjected to an electric cross film voltage, . Here we employ the theoretical expressions derived for the disjoining pressure, D, the film elasticity, F, and the film tension, F, to construct the stability diagram of the film, in the D-. Depending on its state (D, ), the film is stable or is prone to squeezing or bending deformations. For a monooleate film we show how the destruction of the plane film due to a periodic thickness fluctuation (squeezing) is facilitated by two mechanisms: i) lowering of D at fixed ; ii) lowering of at fixed D, provided that the film is in a stable state characterized by D<–7.03×103 dyne/cm2 and >0 mV. Bending of a low tension film (single interface tension s 0.025 dyne/cm1) can be achieved only for >170 mV and D > –8.7 × 104 dyne/cm2. Finally, we demonstrate the existence of a marginal state ( D 0 , 0) where the film is predicted to exhibit strong fluctuations both in the squeezing and in the bending mode.  相似文献   

3.
The new substrates 4-thiouridine and 4-thiothymidine were proposed for spectrophotometric measurement of the activity of uridine (UP) and thymidine (TP) phosphorylases. At pH 7.5, 4-thiouridine has an absorbance maximum at 330 nm, and the difference in extinction coefficient () between 4-thiouridine and 4-thiouracil is 3000 –1cm–1. 4-Thiouridine proved to be a good substrate for UP: the Michaelis ( ) and catalytic (k cat) constants were estimated respectively at 130 M and 49 s–1 at 25°C. Even a greater (5000 M–1cm–1 at 336 nm) was observed for the 4-thiothymidine/4-thiothymine pair.  相似文献   

4.
Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz1H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All the seven tetrasaccharides shared the common core structure GlcA1-3GalNAc1-4GlcA1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GlcA1-3GalNAc(4-sulfate) and/or GlcA1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA1-3GalNAc(4-or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum -N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.Abbreviations NFU National formulary unit - COSY correlation spectroscopy - HOHAHA homonuclear Hartmann-Hahn - 1D or 2D one- or two-dimensional - IdoA l-iduronic acid - GlcA d-gluco-4-enepyranosyluronic acid - Di-0S GlcA1-3GalNAc - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-diS d GlcA(2-sulfate)1-3GalNAc(6-sulfate) - Di-diSE GlcA1-3GalNAc(4, 6-disulfate) - U G, U, 2S, 4S, and 6S represent GlcA, GalNAc, GlcA, 2-O-sulfate, 4-O-sulfate, and 6-O-sulfate, respectively  相似文献   

5.
Summary Determinations of current-voltage relationships are widely employed in the characterization of epithelial sodium transport. In order to determine the protocol dependence of transport parameters in the toad urinary bladder, studies were carried out in the presence and absence of amiloride, an inhibitor of active sodium transport. With symmetric positive and negative perturbations of the transepithelial electrical potential difference (0±100 mV) for 30 sec, the amiloride-sensitive current-voltage (i a -) relationship was near linear over the range –75+100 mV, indicating constancy of the conductance a and the apparent electromotive force E Na, lumped parameters of the standard electrical equivalent circuit model of the active transport system. With a reverse protocol (±1000 mV) or 15 min perturbations thei a - relationships were highly nonlinear. Nonlinearity reflected voltage dependence of parameters: perturbations that increased active transport decreased E Na and increased a, as evaluated from 10 sec perturbations of ; slowing of active transport produced the converse changes. These effects are usefully analyzed in both quasi-steady states and true steady states by means of a detailed equivalent circuit incorporating the significant ionic currents across each plasma membrane. Precise understanding of the significance of a and E Na will require characterization of the partial ionic conductances on perturbation of .  相似文献   

6.
Summary A procedure to reconstitute CF0CF1 proteoliposomes by gel filtration through a Sephadex-column pre-equilibrated with valinomycin and potassium is described. Proteoliposomes reconstituted by this procedure catalyze an ATP-induced pH of 2.5 to 3.5 units. pH was measured with either 9-aminoacridine or with the pH indicator pyranine trapped inside the proteoliposomes. CF0CF1 proteoliposomes prepared by conventional techniques catalyzed an ATP-induced formation, but were unable to catalyze an ATP-induced pH even in the presence of valinomycin.The ATP-induced pH was sensitive to uncouplers and energy transfer inhibitors and was increased at low temperatures. It is suggested that ATP-induced pH was observed in these proteoliposomes due to the efficient removal of intravesicular ammonium introduced with the CF0CF1 preparation. The ammonium acted as an internal buffer, and thus prevented an observable pH formation.  相似文献   

7.
The inside-out vesicles of plasma membranes were isolated from pumpkin stem cells, and the kinetics of sucrose efflux induced by the K+-diffusion potential (D) was studied by measuring light transmission. Two phases differing in their rates and duration were identified in D-dependent changes of light transmission. The increase in Delevated the rate and magnitude of the fast phase in light transmission changes but did not markedly affect the rate of the slow phase. These two phases also differed in their sensitivity to inhibitors and to changes in sucrose concentration in the external medium. Measurements of Dduring sucrose transport by means of the fluorescence probe dis-C3-(5) revealed differences in the magnitude of Dand its stability in vesicles loaded with sucrose and mannitol, as well as under the action of inhibitors. The two-phase dependence of sucrose efflux from vesicles on the applied diffusion potential is discussed in the context of modern concepts on the functioning of sucrose carriers in the membranes.  相似文献   

8.
The organic-matter carbon isotope discrimination () of lichens with a wide range of photobiont and/or cyanobiont associations was used to determine the presence or absence of a carbon-concentrating mechanism (CCM). Two groups were identified within the lichens with green algal photobionts. One group was characterised by low, more C4-like values ( < 15), the other by higher, more C3-like values ( > 18). Tri-partite lichens (lichens with a green alga as the primary photobiont and cyanobacteria within internal or external cephalodia) occurred in both groups. All lichens with cyanobacterial photobionts had low values ( < 15). The activity of the CCM, organic-matter values, on-line values and gas-exchange characteristics correlated with the presence of a pyrenoid in the algal chloroplast. Consistent with previous findings, lichens with Trebouxia as the primary photobiont possessed an active CCM while those containing Coccomyxa did not. Organic values for lichens with Stichococcus as the photobiont varied between 11 and 28. The lichen genera Endocarpon and Dermatocarpon (Stichococcus + pyrenoid) had C4-like organic values ( = 11 to 16.5) whereas the genus Chaenotheca (Stichococcus — pyrenoid) was characterised by high C3-like values ( = 22 to 28), unless it associated with Trebouxia ( = 16). Gas-exchange measurements demonstrated that Dermatocarpon had an affinity for CO2 comparable to those species which possessed the CCM, with K0.5 = 200–215 1 · 1–1, compensation point () = 45–48 l · l–1, compared with K0.5 = 195 1 · 1–1, = 441 · 1–1 for Trebouxioid lichens. Furthermore, lichens with Stichococcus as their photobiont released a small pool (24.2 ± 1.9 to 34.2 ± 2.5 nmol · mg–1 Chl) of inorganic carbon similar to that released by Trebouxioid lichens [CCM present, dissolved inorganic carbon (DIC) pool size = 51.0 ± 2.8 nmol · mg–1 Chl]. Lichens with Trentepohlia as photobiont did not possess an active CCM, with high C3-like organic values ( = 18 to 23). In particular, Roccella phycopsis had very high on-line values ( = 30 to 33), a low affinity for CO2 (K0.5 = 400 1 · 1–1, = 120 1 · –1) and a negligible DIC pool. These responses were comparable to those from lichens with Coccomyxa as the primary photobiont with Nostoc in cephalodia (organic = 17 to 25, on-line = 16 to 21, k0.5 = 388 1 · 1–1, = 85 1 · 1–1, DIC pool size = 8.5 ± 2.4 nmol · mg–1 Chl). The relative importance of refixation of respiratory CO2 and variations in source isotope signature were considered to account for any variation between on-line and organic . Organic was also measured for species of Anthocerotae and Hepaticae which contain pyrenoids and/or Nostoc enclosed within the thallus. The results of this screening showed that the pyrenoid is correlated with low, more C4-like organic values ( = 7 to 12 for members of the Anthocerotae with a pyrenoid compared with = 17 to 28 for the Hepaticae with and without Nostoc in vesicles) and confirms that the pyrenoid plays a fundamental role in the functioning of the CCM in microalgal photobionts and some bryophytes.Abbreviations and Symbols CCM carbon-concentrating mechanism - DIC dissolved inorganic carbon (CO2 + HCO 3 - + CO 3 2- ) - DW dry weight - K0.5 external concentration of CO2 at which half-maximal rates of CO2 assimilation are reached - photobiont photosynthetic organism present in the lichen - Rubisco ribulose-1,5-bisphosphate carboxylase-oxygenase - carbon isotope discrimination (%) - 13C carbon isotope ratio (%) This research was funded by Natural Environment Research Council grant no. GR3/8313. The authors would also like to thank Dr. B. Coppins, Royal Botanic Gardens Edinburgh and Prof. A. Roy Perry, National Museum of Wales, for access to herbarium collections, Dr. T. Booth for confocal microscopy work and Dr. A.J. Richards, University of Newcastle upon Tyne and Dr. O.L. Gilbert, University of Sheffield for identifying bryophytes and lichens respectively. E.S. would particularly like to thank Dr. M. Broadmeadow, The Forestry Authority, Farnham, Surrey, and Cristina Máguas, Universidade de Lisboa, for their advice and expertise at the beginning of the project.  相似文献   

9.
Synopsis The ovary of the domestic pigeon,Columba livia, has been assayed histochemically for the localization of 5-3-hydroxysteroid dehydrogenase (5-3-HSDH), 17-hydroxysteroid dehydrogenase (17-HSDH), 11-hydroxysteroid dehydrogenase (11-HSDH), glucose-6-phosphate dehydrogenase (G6P-DH) and NADH-diaphorase activities during different periods of the reproductive cycle. 5-3-HSDH, 17-HSDH, 11-HSDH, G6P-DH and NADH-diaphorase activity was found in the theca interna of growing, atretic and postovulatory follicles, the granulosa of ovulatory, atretic and postovulatory follicles, and interstitial gland cells during the pre-incubation and the laying periods. During the incubation and squab feeding periods only 5-3-HSDH, G6P-DH and NADH-diaphorase activities were observed in the above mentioned cells. The steroidogenic potential of atretic follicles depends upon the type of atresia a follicle undergoes.  相似文献   

10.
In washed cells of cadmium-sensitive Staphylococcus aureus 17810S oxidizing glutamate, initial Cd2+++ influx via the Mn2+ porter down membrane potential () was fast due to involvement of energy generated by two proton pumps—the respiratory chain and the ATP synthetase complex working in the hydrolytic direction. Such an unusual energy drain for rapid initial Cd2+ influx is suggested to be due to a series of toxic events elicited by Cd2+ accumulation down generated via the redox proton pump: (i) strong inhibition of glutamate oxidation accompanied by a decrease of electrochemical proton gradient ( H +) formation via the respiratory chain, (ii) automatic reversal of ATP synthetase from biosynthetic to hydrolytic mode, which was monitored by a decrease of H +-dependent ATP synthesis, (iii) acceleration of the initial Cd2+ influx down generated the reversed ATP synthetase, the alternative proton pump hydrolyzing endogenous ATP. The primary, cadmium-sensitive targets in strain 17810S seem to be dithiols located in the cytoplasmic glutamate oxidizing system, prior to the membrane-embedded NADH oxidation system. Inhibition by Cd2+ of H +-dependent ATP synthesis and of pH gradient (pH)-linked [14C]glutamate transport is a secondary effect due to cadmium-mediated inhibition of H + generation at the cytoplasmic level. In washed cells of cadmium-resistant S. aureus 17810R oxidizing glutamate, Cd2+ accumulation was prevented due to activity of the plasmid-coded Cd2+ efflux system. Consequently, H +-producing and -requiring processes were not affected by Cd2+.  相似文献   

11.
The behavior of the basic nutrients (NO3, PO4, SiO2) was studied in the estuary of the Razdolnaya River in low and high water, the flow was 4.3 × 106 m3/day and 10.8 × 106 m3/day, respectively. It was shown that within the limits of the euphotic zone the nutrients were characterized by a pronounced nonconservative behavior caused by their removal by phytoplankton in primary production. It was determined that phytoplankton removal of nutrients occurred with ratios C : NO3 : P : Si = 105 : 18 : 1 : 37 and C : NO3 : P : Si = 93 : 11 : 1 : 29 at a respective ratio P : NO3 : Si = 1 : 22 : 140 in low water and P : NO3 : Si = 1 : 17 : 120 in high water. It was also determined that the maximum rate of nutrient removal was 4 times higher in the high water than in the low water. The maximum value of primary production of phytoplankton was 2.5–4.0 gC/m2 day. The estuary area of the Razdolnaya River was specified by rather high production. Such a rate of estuarine primary production, caused by nutrients carried out by the river, being no less than 250 t of dry weight of phytoplankton a day, can provide daily production up to 800 t of biomass in the secondary chain of the ecosystem.Original Russian Text Copyright © 2005 by Biologiya Morya, Zvalinsky, Nedashkovsky, Sagalayev, Tishchenko, Shvetsova.  相似文献   

12.
The reaction of methanol dehydrogenase with cytochrome c L from Methylophaga marina and the reactions of the non-physiological substrates, Wurster's blue and ascorbic acid, with both proteins were studied as a function of temperature (4–32 °C), pressure (1–2000 bar) and ionic strength using the optical high pressure stopped-flow method. The thermodynamic parameters H, S and V were determined for all reactions where electron transfers are involved. These data allowed the determination of the Maxwell relationships which proved the internal thermodynamic consistency of the system under study. A conformational change on the cytochrome c L level was deduced from both breaks in the Arrhenius plots and the variation of the V with temperature.Abbreviations MOPS 4-morpholinepropanesulfonic acid - CHES 2-(cyclohexylamino)ethanesulfonic acid - MDH methanol dehydrogenase - EDTA ethylenedinitrilotetraacetic acid disodium salt - BTB bromothymol blue (3,3-dibromothymolsulfoneph-thalein) - PQQ 2,7,9-tricarboxy-lH-pyrrolo-[2,3f]quinoline-4,5-dione - cytochrome c HH mammalian horse heart cytochrome c  相似文献   

13.
Summary Experiments were performed to determine the factors which contribute to the transmembrane pH gradient (pH) and the potential gradient () in apical plasma membrane vesicles isolated from bovine tracheal epithelium. As indicated by the accumulation of14C-methylamine, the vesicles maintained a pH (inside acidic) which was dependent upon the external pH. The pH was also proportional to the ionic strength of the suspending medium, suggesting that the H+ distribution was dictated by a Donnan potential. Measurements of the distribution of86Rb+ demonstrated an electrical potential gradient across the vesicle membrane, inside negative which was proportional to the medium ionic strength. pH changed in parallel with in response to a variety of imposed conditions. These results are compatible with the existence of a H+ conductance in the vesicle membrane. Thus the endogenous electrical and proton gradients may be manipulated and used as a general experimental tool to complement kinetic analysis in investigations of transport mechanism using isolated vesicle preparations.  相似文献   

14.
The transmembrane proton gradient of the sulfate-reducing bacterium Desulfovibrio desulfuricans strain CSN has been determined by in vivo31P nuclear magnetic resonance (NMR) spectroscopy in the absence of dioxygen. At pH 7.0 in the medium (pHex) the intracellular pH (pHin) was 7.5. By lowering pHex to 5.9 pHin decreased to 7.1. At pHex greater than 7.7 the transmembrane proton gradient (pH) was zero. The uncouplers 3,3,4,5-tetrachlorosalicylanilide (TCS) and carbonylcyanide-m-chlorophenylhydrazone (CCCP), or the permeant anion thiocyanate caused complete dissipation of pH.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - TCS 3,3,4,5-tetrachlorosalicylanilide - MOPS 3-(N-morpholino)-propanesulfonic acid - P i inorganic phosphate - pH in (pHex) intracellular (extracellular) pH - pH transmembrane proton gradient (pHin-pHex) - electrochemical membrane potential - chemical shift in parts per million - NMR nuclear magnetic resonance  相似文献   

15.
The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C161) of aerobically grown O. limnetica was shown to contain both the 7 (79%) and 9 (21%) isomers, while the octadecenoic (C181) acid was entirely the 9 acid. Incorporation of [2-14C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the 7 and 9 C161 and the 9 C181. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both 7 and 9 C161 and 9 and 11 C181. The synthesis of these isomers is characteristic of a bacterialtype, anaerobic pathway.Abbreviations DCMU 3(3,4-dichlorophenyl)-1,1-dimethylurea - MFA monounsaturated fatty acid  相似文献   

16.
Using permeability to labeled glucose as a criterion of stability for liposomal membranes, a comparative study on stabilizing properties of different sterols and triterpenes in phospholipid bilayer has been carried out as well as on structural peculiarities of sterols responsible for membranolytic properties of cucumarioside G1 from the cucumaria Eupentacta fraudatris. Stabilizing action of the studied sterols and triterpenoides incorporated in the bilayer decreases in the following order: cholesterol sulfate > cholesterol > 5-sterols > -sitosterol > ergosterols > 7-sterols > epicholesterol > pregnane > androstane > coprosterol > 14-methylcholest-9(11)-en-3-ol > 4, 14-dimethylcholest-9(11)-en-3-ol > holothurinogenin A1 > glucoside of cholesterol > -xylosidase of 7-sterols > betulin > protopanaxatriol > phosphatidylcholine liposomes without sterol > protopanaxadiol > oleanolic acid. Sterol-dependent membranolytic cucumarioside G1 practically loses its ability to increase permeability of phospholipid membranes containing sterols obtained from this holothuria as well as coprosterol, epicholestrol, sulfated and glycosylated forms of sterols. The obtained results confirm the sterol hypothesis of the mechanism of membranotropic action of holothuria glycosides and of resistance to them of holothuria cell membranes.  相似文献   

17.
The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency c was varied by a metronome, and scaled to the eigenfrequency v of the coupled system K was assumed to vary inversely with c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is c/v rather than c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.  相似文献   

18.
The enzyme 6-desaturase is responsible for the conversion of linoleic acid (18:2) to -linolenic acid (18:3). A cyanobacterial gene encoding 6-desaturase was cloned by expression of a Synechocystis genomic cosmid library in Anabaena, a cyanobacterium lacking 6-desaturase. Expression of the Synechocystis 6-desaturase gene in Anabaena resulted in the accumulation of -linolenic acid (GLA) and octadecatetraenoic acid (18:4). The predicted 359 amino acid sequence of the Synechocystis 6-desaturase shares limited, but significant, sequence similarity with two other reported desaturases. Analysis of three overlapping cosmids revealed a 12-desaturase gene linked to the 6-desaturase gene. Expression of Synechocystis 6-and 12-desaturase in Synechococcus, a cyanobacterium deficient in both desaturases, resulted in the production of linoleic acid and -linolenic acid.  相似文献   

19.
Summary An approximate method to determine sample size for the estimation of population variance, 2, is given. The estimate of 2 is denoted as s2 . Based on the assumption of a normal distribution for (s2/2–1), the sample size is approximately equal to 20,000 z2 p,/k2; where z is a standard normal deviate, p is the probability that s2 ( 100¦s22¦/2) is less than, or equal to, a critical value k, and k (measured as gDs2) is the desired precision of s2 .The expected value of s2, with respect to sample size, and the expected cumulative frequencies of s2 over sample size for various k values are given. Their goodness of fit to the observed results was satisfactory except for populations that were different from normal. The observed values were taken from a study on four yield components in five sugarcane polycross progenies, grown in two contrasting environments over 2 years in three selection stages.The expected s2 was found to be independent of the population coefficient of variance.Research suppoted in part by USDA, ARS, grant #12-14-5001-34. Published with the approval of the Director as Paper No. 412 in the Journal Series of the Experiment Station, Hawaiian Sugar Planters' Association.  相似文献   

20.
By means of reaction calorimetry we measured the apparent enthalpy change, Happ, of the binding of Mn2+-ions to goat -lactalbumin as a function of temperature. The observed Happ can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat -lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (H, G, S, Cp) into the binding and conformational contributions. By circular dichroism we showed that NH 4 + -ions, upon binding to bovine a-lactalbumin, induce the same conformational change as do Na+ and K+: the binding constant equals 98 ± 9 M–1.Abbreviations BLA bovine -lactalbumin - GLA goat -lactalbumin - HLA human -lactalbumin - CD circular dichroism Offprint requests to: H. Van DaelDeceased  相似文献   

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