327 research outputs found
Molecular gyroscopes and biological effects of weak ELF magnetic fields
Extremely-low-frequency magnetic fields are known to affect biological
systems. In many cases, biological effects display `windows' in biologically
effective parameters of the magnetic fields: most dramatic is the fact that
relatively intense magnetic fields sometimes do not cause appreciable effect,
while smaller fields of the order of 10--100 T do. Linear resonant
physical processes do not explain frequency windows in this case. Amplitude
window phenomena suggest a nonlinear physical mechanism. Such a nonlinear
mechanism has been proposed recently to explain those `windows'. It considers
quantum-interference effects on protein-bound substrate ions. Magnetic fields
cause an interference of ion quantum states and change the probability of
ion-protein dissociation. This ion-interference mechanism predicts specific
magnetic-field frequency and amplitude windows within which biological effects
occur. It agrees with a lot of experiments. However, according to the
mechanism, the lifetime of ion quantum states within a protein
cavity should be of unrealistic value, more than 0.01 s for frequency band
10--100 Hz. In this paper, a biophysical mechanism has been proposed that (i)
retains the attractive features of the ion interference mechanism and (ii) uses
the principles of gyroscopic motion and removes the necessity to postulate
large lifetimes. The mechanism considers dynamics of the density matrix of the
molecular groups, which are attached to the walls of protein cavities by two
covalent bonds, i.e., molecular gyroscopes. Numerical computations have shown
almost free rotations of the molecular gyros. The relaxation time due to van
der Waals forces was about 0.01 s for the cavity size of 28 angstr\"{o}ms.Comment: 10 pages, 7 figure
New mechanism of solution of the -problem in magnetobiology
The effect of ultralow-frequency or static magnetic and electric fields on
biological processes is of huge interest for researchers due to the resonant
change of the intensity of biochemical reactions although the energy in such
fields is small. A simplified model to study the effect of the weak magnetic
and electrical fields on fluctuation of the random ionic currents in blood and
to solve the problem in magnetobiology is suggested. The analytic
expression for the kinetic energy of the molecules dissolved in certain liquid
media is obtained. The values of the magnetic field leading to resonant effects
in capillaries are estimated. The numerical estimates showed that the resonant
values of the energy of molecular in the capillaries and aorta are different:
under identical conditions a molecule of the aorta gets times less
energy than the molecules in blood capillaries. So the capillaries are very
sensitive to the resonant effect, with an approach to the resonant value of the
magnetic field strength, the average energy of the molecule localized in the
capillary is increased by several orders of magnitude as compared to its
thermal energy, this value of the energy is sufficient for the deterioration of
the chemical bonds.Comment: 10 pages, Accepted to the Journal Central European Journal of Physic
A human CCT5 gene mutation causing distal neuropathy impairs hexadecamer assembly in an archaeal model
Chaperonins mediate protein folding in a cavity formed by multisubunit rings. The human CCT has eight
non-identical subunits and the His147Arg mutation in one subunit, CCT5, causes neuropathy. Knowledge
is scarce on the impact of this and other mutations upon the chaperone’s structure and functions. To make
progress, experimental models must be developed. We used an archaeal mutant homolog and demonstrated
that the His147Arg mutant has impaired oligomeric assembly, ATPase activity, and defective protein
homeostasis functions. These results establish for the first time that a human chaperonin gene defect can be
reproduced and studied at the molecular level with an archaeal homolog. The major advantage of the system,
consisting of rings with eight identical subunits, is that it amplifies the effects of a mutation as compared
with the human counterpart, in which just one subunit per ring is defective. Therefore, the slight deficit of a
non-lethal mutation can be detected and characterized
Alpha helix-coil phase transition: analysis of ab initio theory predictions
In the present paper we present results of calculations obtained with the use
of the theoretical method described in our preceding paper [1] and perform
detail analysis of alpha helix-random coil transition in alanine polypeptides
of different length. We have calculated the potential energy surfaces of
polypeptides with respect to their twisting degrees of freedom and construct a
parameter-free partition function of the polypeptide using the suggested method
[1]. From the build up partition function we derive various thermodynamical
characteristics for alanine polypeptides of different length as a function of
temperature. Thus, we analyze the temperature dependence of the heat capacity,
latent heat and helicity for alanine polypeptides consisting of 21, 30, 40, 50
and 100 amino acids. Alternatively, we have obtained same thermodynamical
characteristics from the use of molecular dynamics simulations and compared
them with the results of the new statistical mechanics approach. The comparison
proves the validity of the statistical mechanic approach and establishes its
accuracy.Comment: 34 pages, 12 figure
Ab initio theory of helix-coil phase transition
In this paper we suggest a theoretical method based on the statistical
mechanics for treating the alpha-helix-random coil transition in alanine
polypeptides. We consider this process as a first-order phase transition and
develop a theory which is free of model parameters and is based solely on
fundamental physical principles. It describes essential thermodynamical
properties of the system such as heat capacity, the phase transition
temperature and others from the analysis of the polypeptide potential energy
surface calculated as a function of two dihedral angles, responsible for the
polypeptide twisting. The suggested theory is general and with some
modification can be applied for the description of phase transitions in other
complex molecular systems (e.g. proteins, DNA, nanotubes, atomic clusters,
fullerenes).Comment: 24 pages, 3 figure
A study of the centrally produced baryon-antibaryon systems in pp interactions at 450 GeV/c
A study of the centrally produced ppbar, ppbarpi, ppbarpipi and lambda lambda
channels has been performed in pp collisions using an incident beam momentum of
450 GeV/c. No significant new structures are observed in the mass spectra,
however, important new information on the production dynamics is obtained. A
systematic study of the production properties of these systems has been
performed and it is found that these systems are not produced dominantly by
double Pomeron exchange.Comment: 13 pages, Latex, 4 Figure
A study of pseudoscalar states produced centrally in pp interactions at 450 GeV/c
A study has been made of pseudoscalar mesons produced centrally in pp
interactions. The results show that the eta and etaprime appear to have a
similar production mechanism which differs from that of the pi0. The production
properties of the eta and etaprime are not consistent with what is expected
from double Pomeron exchange. In addition the production mechanism for the eta
and etaprime is such that the production cross section are greatest when the
azimuthal angle between the pT vectors of the two protons is 90 degrees.Comment: 11 pages, Latex, 3 Figure
A measurement of the branching fractions of the f1(1285) and f1(1420) produced in central pp interactions at 450 GeV/c
A study of the f1(1285) and f1(1420) produced in central pp interactions has
been performed. For the first time in a single experiment the branching
fractions of both mesons in all major decay modes have been determined. Both
the f1(1285) and f1(1420) are consistent with being produced by double Pomeron
exchange.Comment: 15 pages, Latex, 5 Figures, submitted to Physics Letters
A study of the centrally produced phiphi system in pp interactions at 450 GeV/c
The reaction pp to pfps(K+K-K+K-) in which the K+K-K+K- system is centrally
produced has been studied at 450 GeV/c. Phi phi production has been found to
dominate this reaction and is compatible with being produced by double Pomeron
exchange. An angular analysis of the phi phi system favours JPC = 2++ and its
dPT dependence is similar to that observed for glueball candidates.Comment: 11 pages, Latex, 4 Figure
A partial wave analysis of the centrally produced pi0pi0 system in pp interactions at 450 GeV/c
A partial wave analysis of the centrally produced pi0pi0 channel has been
performed in pp collisions using an incident beam momentum of 450 GeV/c. An
unambiguous physical solution has been found. Evidence is found for the
f0(980), f0(1300) and f0(1500) in the the S-wave. and the f2(1270) is observed
dominantly in the D0-wave. In addition, there is evidence for a broad
enhancement in the D-wave below 1 GeV.Comment: 12 pages, Latex, 4 Figure
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