ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A new technique for optical observation of the kinetics of chemical reactions perturbed by small pressure changes (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 883-887 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140415
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Fluorescence correlation spectroscopy. III. Uniform translation and laminar flow (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 361-376 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We extend fluorescence correlation spectroscopy to systems that undergo translation or laminar flow in a sample cell. We include theoretical and experimental results; we consider uniform and nonuniform velocity profiles. Concentration correlation analysis extracts microscopic rate parameters from measurements of the spontaneous concentration fluctutations, which occur even at equilibrium. Fluorescence is one of the most sensitive means of monitoring these fluctuations. Analysis of flowing or translating systems (1) offers a method of measuring number concentrations of selected species, for example, of aggregates or polymers, (2) provides a nonperturbing velocity probe, (3) sometimes allows one to circumvent photolytic degradation, (4) has proved extremely helpful in testing and aliging apparatus for fluorescence correaltion measurement and in verifying theoretical analyses, and (5) may be required for interpretation of results obtained on systems in motion, even though that motion is undesired or initially unsuspected. We include both theoretical and experimental results for combined Poiseuille flow and diffusion in the geometry which is of most practical interest. Theoretical expressions for the much simpler cases of nondiffusive Poiseuille flow as well as uniform flow or translation with or without diffusion constitute limiting cases which are displayed explicitly.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170208
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Simple sequential model for the kinetics of conformational transitions of oligomeric helices and proteins (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1499-1520 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple sequential model is developed which is applicable to the kinetics of melting of some types of oligomeric helices and as an idealization to the kinetics of unfolding of some protein molecules. A procedure is presented for calculating the concentrations of all conformational species as functions of time. The time course of experimentally observable quantities which depend on these concentrations may then be computed.One of the most characteristic features of the model is the distinction between a transient and a steady-state phase. During the latter all molecular parameters change at the same rate, which depends strongly on the difficulty of nucleation and the length of the sequence. Simple approximations to the steady-state rate are discussed in terms of the exact solution. Rates of transient processes dependless strongly on the rate of nucleation and the number of steps and are a more direct reflection of the rates of the rates of the elementary process of propagation. The value of experimental observation of transient process is emphasized.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110713
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Fluorescence correlation spectroscopy. II. An experimental realization (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 29-61 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the first experimental application of fluorescence correlation spectroscopy, a new method for determining chemical kinetic constants and diffusion coefficients. These quantities are measured by observing the time behaviour of the tiny concentration fluctuations which occur spontaneously in the reaction system even when it is in equilibrium. The equilibrium of the system is not disturbed during the experiment. The diffusion coefficients and chemical rate constants which determine the average time behaviour of these spontaneous fluctuations are the same as those sought by more conventional methods including temperature-jump or other perturbation techniques. The experiment consists essentially in measuring the variation with time of the number of molecules of specified reactants in a defined open volume of solution. The concentration of a reactant is measured by its fluorescence; the sample volume is defined by a focused laser beam which excites the fluorescence. The fluorescent emission fluctuates in proportion with the changes in the number of fluorescent molecules as they diffuse into and out of the sample volume and as they are created or eliminated by the chemical reactions. The number of these reactant molecules must be small to permit detection of the concentration fluctuations. Hence the sample volume is small (10-8 ml) and the concentration of the solutes is low (∼ 10-9 M). We have applied this technique to the study of two prototype systems: the simple example of pure diffusion of a single fluorescent species, rhodamine 6G, and the more interesting but more challenging example of the reaction of macromolecular DNA with the drug ethidium bromide to form a fluorescent complex. The increase of the fluorescence of the ethidium bromide upon formation of the complex permits the observation of the decay of concentration fluctuations via the chemical reaction and consequently the determination of chemical rate constants.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130103
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Fluorescence correlation spectroscopy. I. Conceptual basis and theory (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 1-27 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a method for determining chemical kinetic constants and diffusion coefficients by measuring the rates of decay of spontaneous concentration fluctuations. The equilibrium of the system is not disturbed during the measurement. We measure the number of molecules of a specified type in a defined open volume as a function of time and compute the time course of the deviations from the thermodynamic mean concentration. The method is based on the principle that the rates of decay of spontaneous microscopic fluctuations are determined by the same phenomenological rate coefficients as those of macroscopic departures from equilibrium which result from external perturbations. Hence, an analysis of fluctuations yields the same chemical rate constants and diffusion coefficients as are measured by conventional procedures. In practice the number of the specified molecules is measured by a property such as absorbance or fluorescence which is specific and sensitive to chemical change. The sample volume is defined by a light beam which traverses the cell. As the molecules appear in or disappear from the light beam, either due to diffusion or chemical reaction, their concentration fluctuations give rise to corresponding fluctuations of the intensity of absorbed or emitted light. This paper presents the theory needed to derive chemical rate constants and diffusion coefficients from these fluctuations in light intensity. The theory is applied to three examples of general interest: pure diffusion in the absence of chemical reaction; the binding of a small rapidly diffusing ligand to a larger slowly diffusing macromolecule; and a unimolecular isomerization. The method should be especially useful in studying highly cooperative systems, relatively noncooperative systems with intermediate states closely spaced in free energy, small systems, and systems not readily subject to perturbations of state.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130102
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The strand-separation transition of T2 bacteriophage DNA (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 797-824 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Strand separation of T2 DNA has been investigated in a helix-destabilizing solvent. Temperature-shift experiments in which the conformation of the DNA is monitored by its viscosity, sedimentation behavior, and kinetics of helix formation show that a well-defined strand-separation transition follows the helix-coil transition usually observed by changes in absorbance. For T2 DNA, this strand-separation transition is 70% as broad as the helix-coil transition, and is characterized by extremely slow kinetics of conformational change in the population. Strand separation requires the expansion of the two-stranded coil observed at the end of the helix-coil transition. This expansion is apparently coupled with the disurption of the last remaining base pairs in the molecule. The expansion process increases the viscosity, and can be readily followed as a function of time and/or temperature. Subsequent separation of the expanded form into complementary strands results in a viscosity decrease, the net result of a reduction in hydrodynamic volume and the halving of the molecular weight. Only under conditions where the driving force for strand separation is large are these events at all synchronous in the population. When the kinetics of conformational change are complete in the strand-separation transition, a mixture of expanded forms and separate strands is observed; the breadth of the transition reflects differences in stability with respect to strand separation among the molecules in the population. The transition exhibits hysteresis and is not a reversible equilibrium between double-stranded and single-stranded forms. It appears that renucleation is kinetically forbidden within the strand-separation region.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130415
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Alpha1-adrenergic stimulation and cytoplasmic free calcium concentration in cultured renal proximal tubular cells: Evidence for compartmentalization of quin-2 and fura-2 (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 128 (1986), S. 466-474 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study was designed to examine the role of changes in cytoplasmic free calcium concentration ([Ca2+]i) during the response to α1-adrenergic agonists in cultured renal proximal tubular cells. Experiments were carried out on primary cultures of canine proximal tubular cells grown in defined culture medium on a solid support, on collagen-coated polycarbonate membranes, or on collagen-coated glass coverslips. Quin-2 and fura-2 were used to monitor [Ca2+]i. The basal level of [Ca2+]i was 101 nM, as measured with quin-2, and 122 nM, as determined using fura-2. Fluorescence flow cytometry revealed that about 85% of the population of proximal tubular cells responded to phenylephrine with an increase in [Ca2+]i. Phenylephrine (10-5 M) caused an immediate actual increase in [Ca2+]i by 18 and 24%, as determined with quin-2 and fura-2, respectively, with the peak increase in [Ca2+]i averaging 22% and 44% over the basal level (180-300 sec). This effect did not require extracellular calcium. The effect of phenylephrine was abolished by prazosin and verapamil. Fluorescence microscopy of quin-2 or fura-2 loaded cells revealed punctate areas of fluorescence within the cytoplasm suggesting vesicular uptake of the dyes. Pinocytotic entrapment of the dyes was demonstrated by the transfer of cell-impermeant fura-2 across tubular cell monolayers mounted in Ussing chambers. The transfer of the dye was similar to that of a marker of fluid-phase pinocytosis, Lucifer Yellow (LY). This pinocytotic entrapment of Ca2+-indicators would lead to underestimation of the actual calcium transients. Microfluorometric study of single proximal tubular cells “scrape-loaded” with fura-2 revealed a four-fold increase in [Ca2+]i concentration following stimulation with phenylephrine.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041280316
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Analysis of cell surface interactions by measurements of lateral mobility (1979)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 12 (1979), S. 481-489 
    Details
    ISSN: 0091-7419
    Keywords: fluorescence photobleaching ; cell surface ; cytoskeleton ; lateral mobility ; membrane interactions ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Interactions of cell surface components with one another and with structures inside and outside the cell may have important physiological functions in the transmission of signals and the assembly of specialized structures. These interactions may be detected and analyzed through their effects on the lateral mobility of cell surface molecules. Measurements by a fluorescence photobleaching method have shown that in general lipid-like molecules diffuse rapidly and freely through the plasma membrane, whereas proteins move much more slowly or appear to be immobile. This dichotomy has been supposed to result from forces beyond the viscosity of the lipid bilayer, which specifically retard the diffusion of membrane proteins. This general picture should be qualified, however, by noting that the lateral mobility of lipid-like molecules can be influenced in detail by changes in the state of the plasma membrane such as result from mitosis or fertilization. The interactions of cell surface proteins that limit their lateral mobility are unknown. The effects of binding concanavalin A to localized regions of cell surface show that these interactions can vary in subtle and complex ways. It may soon be useful to interpret mobility experiments in terms of simple reaction models that attempt to describe surface interactions in physicochemical terms. More experimental data are needed to carry out this program and to relate interactions that affect mobility to the structural connections between cell surface components and the cytoskeleton, which have been detected by biochemical methods and electron and immunofluorescence microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400120408
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...