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  • Chemistry  (1)
  • Detergents  (1)
  • Molecular biophysics  (1)
  • Studies of specific liquid structures  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The role of solvent-induced forces in biomolecular function and stability (1993)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 443-450 
    Details
    ISSN: 0392-6737
    Keywords: Molecular biophysics ; Thermodynamics of solutions ; Liquid-liquid transitions ; Macromolecular and polymer solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Solvent-induced forces (SIFs) have been for a long time erroneously related to the presence of more or less uniform “hydration shells”, consisting of more or less permanently bound water molecules. As such misconceptions fade away, it becomes clear that hydration should be viewed statistically and in terms of topological rather than geometric order, and that minor changes (due to solutes) in the structural-rearrangement times of the solvent can reflect major effects in SIFs. Recent work on SIFs at our laboratory, here critically summarized, shows: i) Precisely localized average intramolecular SIFs adjusting the operation of a protein to just what is physiologically required. ii) The involvement of SIFs in the thermodynamic stability of biomelecular solutions and “soups” and related fluctuation behaviour. Sustained, undamped fluctuations occurring in the instability region, and also subcritical ones, occurring close to (yet, not in) the instability region, have been shown to be capable of triggering important concentration- dependent biomolecular processes, iii) The involvement of large numbers of water molecules (of the order of 100) in intra- and interbiomolecular SIFs. This dramatically expands the dimensionality and extension of the functional phase space and helps understand for the first time the extraordinary thermodynamic functional stability of biomolecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02456926
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  • 2
    Electronic Resource
    Electronic Resource
    Near-i.r. Absorption of H2O and D2O in the liquid and supercooled range (1983)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 1239-1253 
    Details
    ISSN: 0392-6737
    Keywords: Studies of specific liquid structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si riportano risultati sugli spettri di assorbimento i.r. di H2O e D2O fino alla regione di temperature del liquido sopraraffreddato. L'andamento dell'assorbanza a frequenza costante in funzione della temperatura non mostra alcuna indicazione di comportamento anomalo. Al contrario, quando gli spettri sono analizzati con metodo di deconvoluzione, si osserva un comportamento di tipo esponente critico, che correla straordinariamente bene con quello mostrato dalle proprietà di trasporto. I risultati sono discussi anche in relazione ai piú recenti modelli di struttura dell'acqua, derivanti dai risultati di simulazione e dai calcoli di connettività.
    Abstract: Резюме Приводятся результаты для спектров инфракрасного поглощения H2O и D2O для температур переохлажденной жидкости. Не обнаружено аномального поведения, когда поглощательная способность при заданной частоте изучается как функция темпетатуры. Напротив, при анализе спектров с помощью спектральных методов конволюции наблюдается поведение типа критической экспоненты, которое коррелирует с поведением, определяемым транспортыми свойствами. Полученные результаты обсуждаются в связи с недавними моделями структуры воды, полученными на основе моделирования молекулярной динамики и нычислений связности.
    Notes: Summary Results are reported on near-i.r. absorption spectra of H2O and D2O down to the temperature region of supercooled liquid. No anomalous behaviour is observed when the absorbance at any given frequency is studied as a function of temperature. A critical-exponent behaviour strikingly correlating with that exhibited by transport properties is instead observed when spectral deconvolution methods are used. Results are discussed in relation with current views on water structure, based on molecular-dynamics simulation results and connectivity calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460209
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  • 3
    Electronic Resource
    Electronic Resource
    Physics and biophysics of solvent induced forces: hydrophobic interactions and context-dependent hydration (1998)
    Springer
    European biophysics journal 27 (1998), S. 183-196 
    Details
    ISSN: 1432-1017
    Keywords: Key words Protein folding/unfolding ; Charge-apolar solute interaction ; Molecular dynamics ; Protein coagulation ; Detergents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Solvent induced forces (SIFs) among solutes derive from solvent structural modification due to solutes, and consequent thermodynamic drive towards minimization of related free energy costs. The role of SIFs in biomolecular conformation and function is appreciated by observing that typical SIF values fall within the 20–200 pN interval, and that proteins are stable by only a few kcal mol–1 (1 kcal mol–1 corresponds to 70 pN Å). Here we study SIFs, in systems of increasing complexity, using Molecular Dynamics (MD) simulations which give time- and space-resolved details on the biologically significant scale of single protein residues and sidechains. Of particular biological relevance among our results are a strong modulability of hydrophobic SIFs by electric charges and the dependence of this modulability upon charge sign. More generally, the present results extend our understanding of the recently reported strong context-dependence of SIFs and the related potential of mean force (PMF). This context-dependence can be strong enough to propagate (by relay action) along a composite solute, and to reverse SIFs acting on a given element, relative to expectations based on its specific character (hydrophobic/ philic, charged). High specificity such as that of SIFs highlighted by the present results is of course central to biological function. Biological implications of the present results cover issues such as biomolecular functional interactions and folding (including chaperoning and pathological conformational changes), coagulation, molecular recognition, effects of phosphorylation and more.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050125
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  • 4
    Electronic Resource
    Electronic Resource
    Time-Resolved study of network self-organization from a biopolymeric solution (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 859-868 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Time-resolved studies of network self-organization from homogeneous solutions of the representative biostructural polymer agarose are presented. Solutions are temperature quenched and observed by several techniques. Consistent with previous suggestions by the authors, experiments at concentrations up to about 1.75% w/v provide direct kinetic evidence for the occurrence of at least two distinct processes, leading, in sequence, to self-assembly. These are as follows: (a) a liquid-liquid phase separation of the solution occurring via spinodal demixing and resulting in two sets of regions that have, respectively, higher and lower than average concentrations of random-coiled polymers; and (b) the subsequent 2 coils → double helix transition and accompanying cross-linking and gelation (due to branching of double helices), occurring in the high-concentration regions. The size of the high-concentration regions depends upon agarose concentration and quenching temperature, and is in the range from a fraction of micrometers to a few micrometers, in agreement with earlier experiments. Bundling of the double-helical segments is known to follow self-assembly and can be considered as a third step (gel curing). This follows from the thermo-dynamic instability of the helical segments in the solvent, behaving as a system of rod-like particles connected by more or less flexible joints.The two processes leading in succession to self-assembly are discussed in terms of a phase diagram consistent with available data. Their time scales differ remarkably. At the end of the first process, all polymers remain random coiled and freely drifting. Much later coil-helix transition is observed, always in coincidence with polymer cross-linking and gelation. The enhancement of concentration of random-coiled polymers in specific regions of the sol caused by spinodal demixing is thus a prerequisite for self-assembly of these biostructural gels in the concentration interval studied. Conceptually, concentration enhancements of this type can provide a new pathway for promotion of functional biomolecular interactions even at very low average concentrations. The mechanism will work identically if the region of instability is reached by varying the polymer concentration (e.g., by biosynthesis), rather than by temperature quenching.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310706
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    Paper (German National Licenses)
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