The Dynamics of Irreversible Evaporation of a Water–Protein Droplet and the Problem of Structural and Dynamic Experiments with Single Moleculesстатья
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Дата последнего поиска статьи во внешних источниках: 2 ноября 2016 г.
Авторы:
Shaitan K.V. ,
Armeev G.A. ,
Shaytan A.K.
Журнал:
Biophysics
Том:
61
Номер:
2
Год издания:
2016
Издательство:
Maik Nauka/Interperiodica Publishing
Местоположение издательства:
Russian Federation
Первая страница:
177
Последняя страница:
184
DOI:
10.1134/S0006350916020172
Аннотация:
Abstract—The effect of isothermal and adiabatic evaporation on the state of a water–protein droplet is discussed.
The considered problem relates to the design of various approaches for structural and dynamic experiments
with single molecules involving X-ray lasers. The delivery of the sample into the X-ray beam is performed
by a microdroplet injector in these experiments; and the approach time is in the microsecond range. A version
of molecular-dynamics simulation for all-atom modeling of an irreversible isothermal evaporation process is
developed. The parameters of the isothermal evaporation of a water–protein droplet that contains sodium and
chloride ions at concentrations of approximately 0.3 M have been determined in computational experiments for
different temperatures. The in silico experiments showed that the energy of irreversible evaporation at the initial
stages of the process was virtually the same as the specific heat of evaporation for water. An exact analytical solution
of the problem for the kinetics of irreversible adiabatic evaporation has been obtained in the limit of the high
heat conductivity of the droplet (or a droplet size not exceeding ~100 Å). This solution contains parameters that
were derived from simulation of the isothermal evaporation of the droplets. The kinetics of the evaporation and
adiabatic cooling of the droplet were shown to be scalable according to the size of the droplet. Estimation of the
rate of freezing of the water–protein droplet upon adiabatic evaporation in a vacuum chamber revealed the
necessity of using additional procedures for stabilizing the temperature in the droplet nucleus that contains the
protein molecule. Isothermal or quasi-isothermal conditions are more favorable for the investigation of macromolecular
structural rearrangements that are related to the functioning of the object. However, the effects of
dehydration and a sharp increase in the ionic strength of the aqueous microenvironment of the protein must be
taken into account in this case.
Keywords: molecular dynamics, droplet evaporation, water–protein systems, experiments with single molecules,
X-ray free electron lasers (XFEL)
DOI: 10.1134/S0006350916020172
Перевод статьи Биофизика, Original Russian Text © K.V. Shaitan, G.A. Armeev, A.K. Shaytan, 2016, published in Biofizika, 2016, Vol. 61, No. 2, pp. 213–221.
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Droplet_engl.pdf
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21 июня 2016
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