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Energetics of the Contraction Cycle in Muscle.

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the inclusion compound, the dodecamolybdate ion breaks
down into the hexamolybdate ion, thus liberating the indicared.
tor and coloring the solution
which is still acidic
Inclusion compounds can condense to form true heteropolyacids which are purely inorganic chelate complexes. Naturally only such materials are included or complexed which
by virtue of their size, structure, and coordinating ability
can pass into the hollows within the isopolyanion.
[GDCh-Ortsverband Braunschweig (Germany).
January 20th, 19641
[VB 784/125 lE]
~
German version: Angew. Chem. 76, 236 (1964)
Adsorption Phenomena at GasiSolid
Interfaces at Low Gas Pressures
N . Hnnserz, Aachen (Germany)
The isotherms for physical adsorption of argon o n different
adsorbents in ultrahigh vacuum d o not yield the proportionality between pressure and amount of gas absorbed predicted
for low coverages. Down to a fraction of the monolayer of
10-6 and at relative equilibrium pressures p/po of 10-12 or
p = 10-10 mm, a parabolic isotherm is observed, which may
be ascribed to thermodynamic heterogeneity of the surface.
Experiments suggest that at even lower coverages linear isotherms are obtained and that a t very low coverages there
are at least 104 units of very sparsely occupied surface for
each unit of closely occupied surface.
The chemisorption of gases o n pure metallic surfaces takes
place very rapidly and cannot be measured in conventional
gas-volumetric apparatus. By means of a n “open apparatus”
(with continuous admission of gas), it was possible to observe
the rate of adsorption over many orders of magnitude. For
instance, for carbon monoxide on zirconium films obtained
by evaporation, it amounts, at low coverage, to about half
the maximum possible rate of impact, which may be calculated
from gas kinetics. The rate of adsorption of metal powders
with relatively pure surfaces - obtainable from some tranis therefore desition metals by heat treatment in wcuo
termined by the Knudsen molecular flow. If a suitable pore
structure is generated in these metal powders, they are
adequate for the production of compact arrangements that
show large adsorptive capacities for gases at very high adsorptionrates and may be used as sorption pumps or getters.
[GDCh-Ortsverband Berlin (Germany),
[VB 7911133 1El
January 21st, 19641
~
German version: Angew. Chem. 76, 308 (1961)
Energetics of the Contraction Cycle in Muscle
W. F. H . M. Mommaerts, Los Angeles, Calif. (U.S.A.)
Present day knowledge of the biochemical basis of the energetics of muscle contraction rests mainly upon the experimental possibility of interrupting a muscle contraction at
any desired stage by rapid freezing of the specimen and of
comparing the chemical composition of the latter with that
of a n unstimulated control. Technically, this has become
possible through methodological developments made in our
laboratory during the last decade; the limit of the method is
set by statistical fluctuations between the compositions of
muscles within a pair. Thus, frog sartorius muscle forms 0.4
ymole of creatine and phosphate in a single tetanic contraction of 400 msec, and the same figure is obtained for the
activation metabolism per contraction in a series of brief
tetari, extrapolated to conditions of zero work performance,
although there are cases where this behavior has not yet been
demonstrated. When work is done, more hposphocreatine
is broken down.
While these two results, in agreement with work by Cnrlsoir,
account for two categories of energy production, a third,
Angew. Chem. infernaf.Edit. 1 VoI. 3 (1964) 1 No. 4
HiN’s shortening heat, could not be dctectcd in this way.
Since there is good reason to assume the existence of a
shortening heat, representing the dissipational heat of a
work process under non-ideal conditions, this discrepancy
represents one of the urgent problems in this field. The recent
observation by Dnvies of the primary breakdown of ATP is
in accordance with expectations. One interesting aspect of
this work, which we seem able to confirm, is that part of the
activation metabolism occurs in the relaxation phase of the
contraction cycle, while the activation heat occurs earlier.
This finding, too, remains t o be explained.
With such fundamental aspects of the energetic balance still
incompletely explained, it seems premature to try to
account for the energetic problems in molecular terms.
However, a discussion was given of some such questions
with regard to the energetic effects of binding versus splitting
of ATP, of the importance of a specific conformation of
myosin-adenosine triphosphatase, of the participation of
actin, and of the importance of Curie’s theorem in biological
energetics.
[Biochemisches Colloquium, Universitat Heidelberg
(Germany), January 23rd, 19641
[VB 795/128 IE]
German version: Angew. Chcm. 76. 308 (1964)
Scattering and Absorption Coefficients in Diffuse
Reflection of Powdered Materials
G. Kortiim, Tiihingen (Germany)
I n determining “typical color curves” of powdered materials by means of the Kubelka-Munk function
F(R,)=
(1-R,)2/2
R,
=
K/S
it is assumed that the scattering coefficient S is independent of the wavelength, so that the absorption coefficient K becomes proportional to the true absorption coefficient of the absorbing medium. If the multiple scattering of
powders is treated generally on the basis of the Mie theory
[ I ] for simple scattering, it is to be expected that. for particle
diameters d that are very small in comparison with the waveA-4, and for
length i., the scattering coefficient becomes S
particle diameters that are large in comparison with the
wavelength, S becomes independent of A. The scattering
coefficients of reference standards (Aerosil, MgO, NaCI,
CaF2, cracking catalysts, glass powders, etc.) were determined, for the limiting conditions indicated, from the
reflectance and transmittance of very thin powder layers and
,
. For Aerosil samples of varying particle size, for
from R
which d .g A, the scattering coefficients ranged from S-1-2.6
to S -h-3.6.
The exponential -4, characteristic of simple
Rayleigh scattering, was thus not reached, while for d s > . ,
S is in fact independent of the wavelength in the visible and
near ultraviolet regions. For application of the KubelkaMunk theory to the determination of typical color curves of
powders, it follows therefore that no particle size below
2-5 y should be used, if the spectra of adsorbed substances are to be examined. Otherwise, the scattering coefficients of the adsorbent must first be determined.
-
As a n example, the absorption spectrum of graphite on
Aerosil was given from 700 to 250 mp, the scattering coefficients measured being taken into account. It was shown that
the scattering coefficients of the adsorbent are not changed
by admixture of 0.1
graphite, so that the true spectrum
of the adsorbed substance may actually be obtained in this
way with ultrafine adsorbents [*I.
[Chemische Gesellschaft Heidelberg (Germany),
January 21st, 19641
[VB 789/130 IE]
German version: Angew. Chem. 76, 308 (1964)
[l] G. Mie, Ann. Physik 25, 377 (1908).
[*] This work will soon be published i n detail in Zeitschrift f u r
Naturforschung, Section a.
32 I
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