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1.
G. Weill  J. Sturm 《Biopolymers》1975,14(12):2537-2553
Theoretical expressions are derived for the change in the polarized components of the fluorescence, resulting from the orientation of a rigid molecule bearing a chromophore with arbitrary angles for the absorption and transition moments \documentclass{article}\pagestyle{empty}\begin{document}$ \vec \mu _a $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \vec \mu _e $\end{document} with respect to the molecular axis. The break in the symmetry relation HV = VH is related to the tilt angle between \documentclass{article}\pagestyle{empty}\begin{document}$ \vec \mu _a $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \vec \mu _e $\end{document}. The theory is applied to a sonicated DNA–2-hydroxy-4,4′-diamidinostilbene complex, in the blue and red emission bands of this peculiar dye. Simultaneous measurements of linear dichroism and fluorescence lead to the determination of an angle of 47° between a fluorescent bound dye and the DNA axis, with no difference for the blue- and red-emitting species, but confirm the presence of nonfluorescent bound dye in a more perpendicular arrangement.  相似文献   

2.
Circulating neutrophils isolated from patients 3–4 h after a myocardial infarction produced less $ {\rm O}\frac{ \cdot }{{\rm 2}} $ compared with controls, when stimulated with phorbol myrystate acetate or formyl-methionine-leucine-phenylalanine. Three days after the infraction the $ {\rm O}\frac{ \cdot }{{\rm 2}} $ generation elicited by both stimuli further decreased markedly. Seven and 15 days after infarction the $ {\rm O}\frac{ \cdot }{{\rm 2}} $ stimulated production was only slightly lower than or similar to the control values. The neutrophils of infarcted patients showed an augmented latency period before $ {\rm O}\frac{ \cdot }{{\rm 2}} $ production compared with controls in response to exogenous stimuli, particularly three days after infarction. Electron microscopy revealed that the neutrophils isolated from the infarcted patients displayed signs of cell exhaustion with few alterations of the plasma membranes when stimulated with phorbol ester. In contrast, control neutrophils displayed alterations of the plasma membranes characteristic of active neutrophils. The results of this study indicate that the circulating neutrophils appear exhausted and functionally inhibited immediately after myocardial infarction.  相似文献   

3.
In this paper it is shown that if N= \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^{S_h} $\end{document} cihNih, where cih are some non-negative integer numbers and Nih are such incidence matrices that Ah = \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^{S_h} $\end{document} i Nih is a balanced matrix defined by SHAH (1959), for h = 1, 2,…, p, then a block design with an incidence matrix Ñ = [N, N,…,N] is an equi-replicated balanced block design. Here the balance of a block design is defined in terms of the matrix M0 introduced by CALI?SKI (1971).  相似文献   

4.
R T Ingwall  P J Flory 《Biopolymers》1972,11(7):1527-1539
Optical anisotropies γ2 of N-t-butylacetamide (tBA), N-Methylacetamide (MA), and N, N-dimethylacetamide (DMA) have been determined from the Rayleigh ratios for depolarzed scattering by dilute solutions of the amides in p-dioxane. Traceless optical polarizability tensors \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat{\rm \alpha } $\end{document} for the amides are derived from these results in conjunction with the Kerr constant for tBA determined by LeGèvre and co-workers. It is shown that the tensor \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat{\rm \alpha } $\end{document}i for the glycyle unit in a polypeptide chain may be identified with \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat{\rm \alpha } $\end{document}MA . Methods for deriving corresponding tensors for other peptide units are indicated and the traceless polarizability tensor \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat{\rm \alpha } $\end{document} for a polypeptide chain in any specified configuration is formulated.  相似文献   

5.
The phosphate removal in small, completely mixed storage reservoirs (preimpoundment basins) mainly is a function of the production of biomass by the phytoplankton. The knowledge of the critical detention time of the water is the most important premise to the prediction. The critical detention time t̄ is computed from the equation: \documentclass{article}\pagestyle{empty}\begin{document}$ \overline t _c = \frac{1}{{\mu ^* - 0,1}} $\end{document} and the growth rate μ* at a given combination of the light intensity J, temperature T and phosphate concentration P is computed from: \documentclass{article}\pagestyle{empty}\begin{document}$ \mu ^* = \frac{{\mu T \cdot \mu J \cdot \mu P}}{{\mu \max ^2 }}\mu \max \cdot \frac{P}{{K_p + P}}\frac{J}{{K_j + J}}\frac{T}{{T_{opt} }}, $\end{document} (μmax = maximum possible growth rate of the dominant species; Kp, Kj and Topt are constants computed from batch cultures). The quotient \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{\bar t_{act.} }}{{\bar t_c }}(\bar t_{act.} = {\rm actual detention time in the water body)} $\end{document} enables prediction of the phosphate removal. A comparison of the predicted results from semicontinuous cultures and from the preimpoundment basin of the Weida reservoir revealed a satisfactory degree of conformity.  相似文献   

6.
Frost (1987a) proposed an algorithm for estimating the number of missing osteons that correspond to observed osteon population densities (OPD). Such an algorithm should allow more accurate estimates of bone remodeling rates for skeletal remains for which in vivo labeling is not possible. In order to validate the algorithm, it was tested on an autopsy sample of 44 ribs. Estimates of activation frequency. ($ \mathop {\rm \mu }\limits^ - $RC) and bone remodeling rate (Vf,r,t) using the new algorithm are in reasonable agreement with age-matched tetracycline-based values. Although mean values for activation frequencies ($ \mathop {\rm \mu }\limits^ - $RC) and bone formation rate (Vf,r,t) generated by the algorithm were generally lower, they fell below 1 standard error for only an age category that included all ages above the 5th decade. It is now appropriate to apply the algorithm to archaeological skeletal remains. © 1994 Wiley-Liss, Inc.  相似文献   

7.
The ir absorption and CD conformational analyses of solutions of the protected 2–9 fragment of the peptaibol antibiotics emerimicins III and IV \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} (Aib_3 \rlap{--} )L - Val - Gly - L - Leu\rlap{--} (Aib_2 \rlap{--} ) $\end{document} and related short sequences are consistent with the presence of a right-handed α-helix for the octapeptide, while the tri-, tetra-, and pentapeptides adopt a 310-helix, either right- or left-handed, depending on the amino acid sequences. The structural preferences of solid-state \documentclass{article}\pagestyle{empty}\begin{document}$ Z\rlap{--} (Aib_3 \rlap{--} )L - Val - OMe $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ Z\rlap{--} (Aib_3 \rlap{--} )L - Val - Gly - OMe $\end{document} have been determined by x-ray diffraction. In accord with the solution data, incipient 310-helices, formed by two and three β-turns, have been found for the tetra- and pentapeptides, respectively. The tetrapeptide helix has the left-handed screw sense, while that of the pentapetide is right-handed, thus confirming the conclusions of the CD analysis of the solution.  相似文献   

8.
The presence of both book lungs and a tracheal system in many spiders raises the question of the functional significance of this double respiratory system. The present physiological and morphometric study of the house spider (Tegenaria spp.) reveals that the diffusing capacity (Dto2) of the lungs alone suffices during rest and following exercise to meet measured rates of oxygen consumption (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm V}\limits^{\rm.} $\end{document}o2) at driving pressures (ΔPto 2) similar to those calculated for vertebrate lungs. During moulting ΔPto 2 may rise to more than double the vertebrate values, implying the possible insufficiency of book lungs during this critical life phase. Resting \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm V}\limits^{\rm .} $\end{document}o2 is greatest (92 mm3/h · g) during the early morning and lowest (66 mm3/h · g) near midday: during moulting \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm V}\limits^{\rm .} $\end{document}o2 rises to 278.7 mm3/h · g. In spiders recovering from exercise \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm V}\limits^{\rm .} $\end{document}o2 is consistently greater than during rest: neither value is significantly reduced by blockage of the tracheal stigmas. Regression calculations of morphometric values for a hypothetical 100-mg Tegenaria yield a total lung volume of 0.578 mm3, a pulmonary surface area of 69.8 mm2, and a surface-to-volume ratio of 120.89 mm2/mm3. In spite of the similar thickness of the chitinous and hypodermal components of the air-hemolymph barrier (each ca. 0.2 μm in nonmoulting animals), the low permeability of chitin for oxygen makes this layer the greater barrier to diffusion. For a 100-mg specimen Dto2 is 3.5 mm3/h · torr: similar to that of a turtle (Pseudemys) on a gram-body weight basis.  相似文献   

9.
Four commonly used formulae for measuring percentage similarity (PS) of biological communities were tested for their usefulness in relating to two plankton community properties, species proportional differences and total density differences. The formula best combining species proportionality and total density in the expression of PS is new: where min (xi,yi) is the lesser percentage (doubly standardized) of a species in two samples X and Y and where 2 q, 2xi and 2yi are the total quantities of all species in samples 8,X and Y, where \documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_i {z_i } ,\,\sum\limits_i {x_i } \,and\sum\limits_i {y_i } $\end{document} are the total quantities of all species in samples Z, X and Y, respectively. Sample 2 contains the highest density of all species in the set; \documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_i {z_i \, > \,(\sum\limits_i {x_i ,\,} \sum\limits_i {y_i } )} $\end{document}. The new expression of PS is simple to use and has the additional advantage of offering the analyst an unlimited choice of weighting factors or importance values for proportionality of species content and total density. The method has been applied to data from Gravenhurst Bay (Ontario) and effectively demonstrates the consequences of phosphorus loading reductions for phytoplankton communities.  相似文献   

10.
Estimating the dynamics of furbearer populations is challenging because their elusive behavior and low densities make observations difficult. Statistical population reconstruction is a flexible approach to demographic assessment for harvested populations, but the technique has not been applied to furbearers. We extended this approach to furbearers and analyzed 8 yr of age-at-harvest data for American marten (Martes americana) in the Upper Peninsula of Michigan. Marten abundance estimates showed a general downward trend from an estimate of = 1,733.3 animals in 2000 to = 1,163.9 in 2007. The harvest probability of martens increased nearly 5-fold from 0.0542 in 2000 to 0.2637 in 2007, which corresponded to a 5-fold increase in trap-nights. Continued monitoring of martens in the Upper Peninsula, Michigan, and a reassessment of current harvest regulations are necessary given the estimated decreases. Moreover, we do not encourage the use of harvest indices as the sole technique to assess the status and trends of marten and fisher populations. Auxiliary studies in the Upper Peninsula, Michigan, will allow for continued use and improvement in the application of these models. © 2011 The Wildlife Society.  相似文献   

11.
The survival of all aerobic life forms requires the ground-state of molecular oxygen, O2. However, the activation of O2 to reactive oxygen species (ROS) is responsible for universal toxicity. ROS are responsible in deleterious intracellular reactions associated with oxidative stress including membrane lipid peroxidation, and the oxidation of proteins and DNA. Redox-active allelochemicals such as quinones and phenolic compounds are involved in activating O2 to its deleterious forms including superoxide anion free radical, $ {\rm O}_{\rm 2} ^{ \cdot - } $, hydrogen peroxide, H2O2, and hydroxyl radical, $ \cdot {\rm OH} $. Molecular oxygen is also activated in biologically relevant photosensitizing reactions to the singlet form, 1O2. The insect lifestyle exposes them to a broad diversity of pro-oxidant allelochemicals and, like mammalian species, they have developed an elaborate antioxidant system comprised of chemical antioxidants and a bank of antioxidant enzymes. We have found that an insect's antioxidant adaptation to a particular food correlates well with its risk of exposure to potential pro-oxidants. © 1995 Wiley-Liss, Inc.  相似文献   

12.
The effect of enzyme-inhibitor complex formation on the hydration properties of the macromolecular moiety was investigated on the model system of α-chymotrypsin and its Ser-195 tosyl derivative. The primary (A-shell) hydration of the native and modified enzyme was compared by sorption measurements. The secondary (B-shell) hydration water was investigated by differential scanning calorimetry. Tosylation is known to induce pronounced conformational changes in the chymotrypsin molecule. These structural modifications have the following effects on the hydration of the native enzyme. The water binding capacity of the protein surface is significantly increased, as shown by both the calorimetric and the sorption results. The amount of unfreezable water of primary hydration is increased by 50 mol H2O/mol chymotrypsin. The heats (ΔH ) and entropies (ΔS ) of the interaction of water with chymotrypsin are strongly reduced in the modified enzyme. This effect is interpretable by a reduction of the H bonding potential of the protein surface. Parallel to this decrease in δH , the heats of fusion of the secondary hydration water (Qfus) are significantly increased by tosylation (Qfus = 256.2 ± 7.8 and 294.2 ± 4.8 J g?1 H2O for the native and the tosylated enzyme, respectively). This increase in Qfus reflects an increase in the extent of H bonding in the B-shell hydration sphere. These changes in the hydration of the native enzyme, associated with the reaction: native chymotrypsin → tosylchymotrypsin, are interpreted by cooperative phase transitions of water molecules in the primary and secondary hydration water. One of these transitions was found to exhibit a significant, linear enthalpy–entropy compensation effect. The compensation temperature \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} is 290.7 ± 2.8°K. This \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} value agrees well with compensation temperatures reported in the literature for a series of biochemical reactions in aqueous solution (250–320° K). This agreement in \documentclass{article}\pagestyle{empty}\begin{document}$ \hat{\beta} $\end{document} may point to a common source of both compensation phenomena.  相似文献   

13.
For the model y = α + βx + ? (model I) of linear regression we dealt with in KUHNERT and HORN (1980) the determination of a confidence interval for that x0 where the expectation Ey reaches a given value y0. Here we start with realizations of random variables y (i = 1,…, m) being independent of x which are given in addition to the realizations of-y. Now y0 denotes the unknown value of \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^m $\end{document} ciEy and x0 the x-value where the expectation Ey reaches that value y0. For this x0 we give a confidence interval. Applications stem from dose response assays.  相似文献   

14.
Fast growth of industrial microorganisms, such as Corynebacterium glutamicum, is a direct amplifier for the productivity of any growth coupled or decoupled production process. Recently, it has been shown that C. glutamicum when grown in a novel picoliter bioreactor (PLBR) exhibits a 50% higher growth rate compared to a 1 L batch cultivation [Grünberger et al. (2012) Lab Chip]. We here compare growth of C. glutamicum with glucose as substrate at different scales covering batch cultivations in the liter range down to single cell cultivations in the picoliter range. The maximum growth rate of standard batch cultures as estimated from different biomass quantification methods is ${\hat {\mu }} = 0.42\pm 0.03\,{\rm h}^{- 1} $ even for microtiter scale cultivations. In contrast, growth in a microfluidic perfusion system enabling analysis of single cells reproducibly reveals a higher growth rate of ${\hat {\mu }} = 0.62\pm 0.02\,{\rm h}^{- 1} $ . When in the same perfusion system cell‐free supernatant from exponentially grown shake flask cultures is used the growth rate of single cells is reduced to ${\hat {\mu }} = 0.47\pm 0.02\,{\rm h}^{- 1} $ . Likewise, when fresh medium is additionally supplied with 5 mM acetate, a growth rate of ${\hat {\mu }} = 0.51\pm 0.01\,{\rm h}^{- 1} $ is determined. These results prove that higher growth rates of C. glutamicum than known from typical batch cultivations are possible, and that growth is definitely impaired by very low concentrations of byproducts such as acetate. Biotechnol. Bioeng. 2013; 110: 220–228. © 2012 Wiley Periodicals, Inc.  相似文献   

15.
In this article, we consider r observations from a non‐homogeneous censored Markov chain, with transition probability matrix P. For the product estimator of P proposed by Aalen and Johansen (1978) and Phelan (1988), we investigate the behavior of Bayesian bootstrap clones to approximate the sampling distribution of , and then construct approximate confidence interval. It is shown that the approximation based on the random‐weighted distribution is first‐order consistent. The performance of the Bayesian bootstrap clones (BBC) is also discussed by small sample simulation. Finally, we illustrate the BBC procedure in the application to the WHO malaria survey data (cf. Singer and Cohen 1970).  相似文献   

16.
L Yuan  S S Stivala 《Biopolymers》1972,11(10):2079-2089
The effect of dielectric constant (D) of the solvent on the viscosity of heparin was examined using the relation \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _{{\rm sp}} /c = [\eta ]_\infty (1 + k/\sqrt c) $\end{document}, where [η] is the shielded intrinsic viscosity obtained by extrapolating \documentclass{article}\pagestyle{empty}\begin{document}$ \eta _{{\rm sp}} /c\,{\rm vs}{\rm . }\,1/\sqrt c ) $\end{document} to infinite concentration, and k is an interaction parameter independent of the dielectric constant of the solvent. This equation was previously reported by the authors9 for describing the reduced viscosities of strong polyelectrolytes in salt-free polar solvents. It was found that the [η] of heparin increases linearly with increasing dielectric constant of the solvent whereas the k values were, within experimental error, independent of D in the range 54.7 < D < 93.2 examined. Graded hydrolysis of heparin from its acid form (heparinic acid) at 57°C resulted in samples of varying degree of desulfation with corresponding decrease in biological activity. It was found that both [η] and k decrease with increasing desulfation.  相似文献   

17.
Duckling survival is an important component of mallard (Anas platyrhynchos) recruitment and population growth, yet many factors regulating duckling survival are poorly understood. We investigated factors affecting mallard duckling survival in the drift prairie of northeastern North Dakota, 2006–2007. Mammalian meso-predators were removed by trapping on 4 92.3 km2 study sites and another 4 study sites served as controls. We monitored 169 broods using telemetry and periodic resighting, and we modeled cumulative survival to 30 days of age using the nest survival module in Program MARK. Duckling survival was not affected by predator removal ( , 85% CI: 0.182–0.234; , 85% CI: 0.155–0.211) and was only weakly negatively correlated with duckling density. Duckling survival was higher in 2007 ( , 85% CI: 0.193–0.355) than 2006 ( , 85% CI: 0.084–0.252) and increased with total seasonal and semipermanent wetland area and declined with perennial cover in the surrounding landscape. Broods that hatched earlier in the season (especially in 2006) and ducklings that were heavier at hatch also had higher survival. Our estimates of duckling survival are among the lowest reported for mallards and contradict previous research in Saskatchewan that found predator removal increased duckling survival. However, our results are consistent with other studies suggesting that earlier hatch date, increased wetland availability, and better duckling condition lead to increased survival. Management actions that increase wetland density, improve nest success early in the season, and potentially target brood-specific predators such as mink (Neovison vison) would likely lead to higher duckling survival. © 2011 The Wildlife Society.  相似文献   

18.
The relationship between cytosolic concentrations of Ca2+ (Ca) and Na+ (Na) were studied in preparations of rat submandibular and pancreatic acini loaded with the Ca2+-sensitive dye Fura-2 or the Na+-sensitive dye SBFI. Pancreatic acini showed no changes in Na during either transient or persistent changes in Ca. Increases in Ca produced by exposure of submandibular gland acini to carbachol, a muscarinic cholinergic agonist, were followed by an increase in Na after a delay of 5–10 s. When Ca2+ stores were mobilized without Ca2+ influx Na also increased, but in acini loaded with BAPTA, a nonfluorescent Ca2+ chelator, the transient increase in Ca2+ caused by mobilization of stored Ca2+ was virtually abolished, as was the increase in Na. In the presence of ionomycin, increases in Ca were followed by increases in Na. Ca2+-dependent increases in Na were abolished in Na+-free buffer and by the presence of furosemide, a blocker of Na+-K+-2Cl cotransport. In other studies, extracellular ATP (ATPo) produced an increase in Ca and Na. The steady-state increase in Ca was reduced by increasing extracellular Na+ concentrations (Na) in dose-dependent fashion (IC50 = 16.4 ± 4.7 mM Na+). Likewise, increasing Na reduced ATPo-stimulated 45Ca2+ uptake at steady state (IC50 = 15.8 ± 9.2 mM Na+). Changing Na had no effect on carbachol-stimulated increases in Ca. We conclude that, in rat submandibular gland acini, ATPo promotes an increase in Ca and Na via a common influx pathway and that, under physiologic conditions, Na+ significantly limits the ATPo-stimulated increase in Ca. In the presence of carbachol, however, Na rises in Ca-dependent fashion in submandibular gland acini via stimulation of Na+-K+-2Cl cotransport. © 1996 Wiley-Liss, Inc.  相似文献   

19.
Assessing wildlife management action requires monitoring populations, and abundance often is the parameter monitored. Recent methodological advances have enabled estimation of mean abundance within a habitat using presence–absence or count data obtained via repeated visits to a sample of sites. These methods assume populations are closed and intuitively assume habitats within sites change little during a field season. However, many habitats are highly variable over short periods. We developed a variation of existing occupancy and abundance models that allows for extreme spatio-temporal differences in habitat, and resulting changes in wildlife abundance, among sites and among visits to a site within a field season. We conducted our study in sugarcane habitat within the Everglades Agricultural Area southeast of Lake Okeechobee in south Florida. We counted wintering birds, primarily passerines, within 245 sites usually 5 times at each site during December 2006–March 2007. We estimated occupancy and mean abundance of birds in 6 vegetation states during the sugarcane harvest and allowed these parameters to vary temporally or spatially within a vegetation state. Occupancy and mean abundance of the common yellowthroat (Geothlypis trichas) was affected by structure of sugarcane and uncultivated edge vegetation (occupancy = 1.00 [ = 0.96–1.00] and mean abundance = 7.9 [ = 3.2–19.5] in tall sugarcane with tall edge vegetation versus 0.20 [ = 0.04–0.71] and 0.22 [ = 0.04–1.2], respectively, in short sugarcane with short edge vegetation in one half of the study area). Occupancy and mean abundance of palm warblers (Dendroica palmarum) were constant (occupancy = 1.00, = 0.69–1.00; mean abundance = 18, = 1–270). Our model may enable wildlife managers to assess rigorously effects of future edge habitat management on avian distribution and abundance within agricultural landscapes during winter or the breeding season. The model may also help wildlife managers make similar management decisions involving other dynamic habitats such as wetlands, prairies, and even forested areas if forest management or fires occur during the field season. © 2011 The Wildlife Society.  相似文献   

20.
It was found that the cellular Na+-concentration (C) of Lodderomyces elongisporus D is depended on the extracellular K+-concentration (C). The relationship can be described by an equation in the form The function of the natrium ion seem to be to support the utilisation rate of potassium ion at lower extracellular K+-concentration.  相似文献   

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