вход по аккаунту


Federation of European Biochemical Societies.

код для вставкиСкачать
Preparation of Polymethylene by the Reaction of
Diazomethane with Diborane
By Dr. G. H. Dorion, S . E. Polchlopek [*I, and
E. H. Sheers
American Cyanamid Company, Stamford, Conn. (U.S.A.)
( 4 ) , X = 0 ; R = p-phenylene
We have synthetized polymethylene at room temperature by
addition of 1 mmole of diborane in 0.8 ml of anhydrous
tetrahydrofuran[l] to a solution of 16 mmole of diazomethane
in 80 ml of ether. An almost quantitative yield was obtained.
The polymer was highly crystalline when studied by microscopy, melted at 136”C, and was estimated by infrared
spectroscopy to contain less than 1.0 methyl group per 1000
methylene groups. A typical sample contained 1.02 P: boron
and had a molecular weight (ebulliometry, toluene) greater
than 20000.
The significance of this rather simple room-temperature synthesis is that it affords a highly linear polymer. Polyethylenes
show CH3:CH? group ratios of 2:1000 to 33:lOOO 121.
x= 0
75 %, m.p. 174-175 “ C (decornp.)
( 6 ) . X = S; R = 1,4-cycloherylene
92 %, m.p. 213-214OC (decomp.)
carbon monoxide in boiling xylene, react with diisonitriles
in xylene at ca. 150°C to yield derivatives, e . g . (6), of N , N bis-(4-oxot hiazolinylidene)diamines.
Received, April 16th, 1964
12 724/549 IE]
German version: Angew. Chem. 76, 500 (1964)
[ I ] R. Neidlein, Angew. Chem. 76, 440 (1964); Angew. Chem.
internat. Edit. 3, 382 (1964).
[2] R. C. A . New and L. E. Sutton, J. chem. SOC.(London) 1932,
[ 3 ] I . Hagedorn and H . Tonjes, Pharmazie 11, 409 (1956); 12,
570 (1957).
[4] I . Ugi, W . Eetz, U. Fetzer, and K . Opfermann, Chem. Ber. 94,
2814 (1961).
151 J. Goerdeler and H . Horstntann, Chem. Ber. 93, 671 (1960).
Received, April 13th, 1964
[ Z 7251543 IE1
German version: Angew. Chem. 76, 495 (1964)
[*I Present address: Barnes Engineering Co., Stamford, Conn.
(U .S. A.).
[ I ] H. C. Brown: Hydroboration. Benjamin,NewYork 1962,p.94.
[2] A . H . Willbourn, J. Polymer Sci. 34, 569 (1959).
Federation of European Biochemical Societies
The first meeting of this federation, which was founded in
January 1964, took place in London from March 23rd to
25th, 1964. The agenda included colloquia on “The Biochemistry of Chloroplasts” and on “lnborn Errors of Metabolism”,
a symposium on “The Structure and Activity of Enzymes”,
and 139 short papers.
The program on the first day included the Jubilee Lecture of
the British Biochemical Society. E. Lederer, Gif-Sur-Yvette
(France), spoke on the origin and function of some methyl
groups in branched-chain fatty acids. In general, the methyl
groups are derived by direct C-methylation of preformed
molecules, or from propionic acid, isoleucine, or mevalonic
acid. During the biosynthesis of tuberculostearic acid ( 3 )
suggesting the conversion of active methionine into a rnethylene-donating molecule (4)
Similarly, methylation of C-24 in desmosterol ( 5 ) t o give
ergosterol (6) proceeds with retention of only 2 hydrogen
The ethylation of cholesterol (7) that occurs at C-24 to give
p-sitosterol ( 9 ) appears to be in fact a form of double methylation. Biological deutereomethylation gave an intermediate
(8) which was isolated and which on ozonization gave acetaldehyde deuterated o n both carbon atoms.
from the corresponding unsaturated acid ( I ) , the possible
occurrence of a cyclopropane type intermediate (2) was envisaged. However, the bacillus was unable t o convert a synthetic sample of this compound into tuberculostearic acid.
Cyclopropanecarboxylic acids may be biosynthetized from
an unsaturated acid and S-adenosylmethionine. When the
methyl group of the methionine used is fully deuterated, two
of the deuterium atoms are retained in the cyclopropane ring,
A n g e w . Chem. internat. Edit. 1 Vol. 3 (1964)
Nc . 6
In Ascaris lumbricoides, condensation of acetate and propionate moitieszgives a branched fatty acid ( l o ) , and in the preen
f IO)
gland of the goose, the long chain fatty acid ( 1 2 ) is built up
entirely from propionic acid units.
The methyl group of coenzyme Q is known to be derived from
mevalonic acid: this methyl group may play a n important
part in oxidative phosphorylation via a quinone methide.
In the symposium, F. M. Richards, New Haven, Conn.(U.S.A.)
listed some chemical modifications made at specific sites in
ribonuclease in order to study the contribution made by its
various constituent amino acids to the activity of the whole
molecule. Thus, dinitrophenylation of lysine 41 results in
complete loss of enzymatic activity; this in turn affects the
reactivity of lysine 7 towards fluorodinitrobenzene. Mutually
exclusive carboxymethylation of histidines 12 or 119 with
iodoacetic acid also results in marked loss of ribonuclease
activity. It was noted as illustrative of the effect of the tertiary
structure o n the chemical reactivity of constituent amino
acids that three of the tyrosine residues do not ionize in the
usual p H range, only 4 out of 6 of these residues react with
iodine, and methionines 13, 29, 30, and 79 d o not react with
iodoacetic acid.
During recombination of the terminal peptide containing 20
amino acids (S-peptide) with the protein part of the molecule
(S-protein) to give ribonuclease-S, residues 3-1 3 in the peptide are crucial for enzymatic activity in the newly formed
complex. Recombination with S-protein of a n S-peptide in
which methionine 13 has been oxidized to the sulfone gives
a catalytically active complex. However AS for this reaction
is -100 e.u. compared with -150 e.u. when the recombination is carried out with unoxidized S-peptide. It was pointed
out that this methionine is adjacent to position 12 which is
implicated in the enzymatic activity of the molecule and yet
it can be changed by 50e.u. (conformational entropy) without
changing the enzyme’s activity.
S . Moore, New York (U.S.A.) gave evidence that the dimer
of ribonuclease which is enzymatically active and which is
obtained by lyophilization of a 50 %, acetic acid solution of
ribonuclease consists of a head-to-tail fit of two partially uncurled molecules. By carboxymethylation of the dimer with 2
moles of iodoacetic acid, he obtained a new dimer consisting
of 1 molecule of a hitherto inaccessible ribonuclease which i s
carboxymethylated at positions 12 and 119, and one molecule
of active ribonuclease.
Substances which inhibit enzymatic hydrolysis of cytidine
2’,3’-phosphate and protect the enzyme against alk4lation
were reported by A . P. Mathias, London (England). In general, there is good agreement between the Ki values obtained
for each compound in both reactions. The pH activity curves
in organic solvents, the variation with pH of the rate of hydrolysis of cytidine 2’,3’-phosphates, and the results of spectrophotometric and kinetic examinations of the inhibition of
ribonuclease by Znz-i- ions all imply that there are two histidines in the active site. It was suggested that a protonated
imidazole group interacts with the 2’-oxygen of the substrate
and another imidazole in its basic form is hydrogen-bonded
to the attacking water molecule. This view was contested by
H. Witzel, Marburg (Germany) in the resulting discussion
and in a short paper. This worker postulated that the binding
of the enzyme to the substrate involves only the phosphate
group in dianionic form, the two concomitant uositive charges
being supplied by a triprotonated diiniidazole system and the
e-ammonium group of lysine 41.
One-hundredfold purification of an enzyme from pig pancreas which catalyses the reactivation by oxygen of reduced
ribonuclease was described by P. Venetianer, Budapest (Hungary). This enzyme requires a thermostable dialysable cofactor which can be replaced by dehydroascorbic acid.
Amino acid sequences for beef chymotrypsinogen arrived at
by B. Keil, Prague (Czechoslovakia), and B. S. Hartley, Cambridge (England), differ, but both are in agreement over the
relative positions of all five disulfide bridges. Serine 195 and
histidine 57 probably constitute the active site. The catalytic
activity also depends o n the N-terminal isoleucine as was
shown by B. Labouesse, Orsay (France). J . Kraut, La Jolla
(U.S.A.),andD.M. Bluw, Cambridge (England), reported progress on X-ray crystallographic analyses of chymotrypsinogen
and a-chymotrypsin, respectively. Both agree that neither of
these molecules contains a n a-helix. R . A . Oosterbnan, Rijswijk (Holland), described the incubation of chymotrypsin
with its substrate (N-acetyltyrosine ethyl ester) in the presence of H i 8 0 . Subsequent acetylation of the protein and isolation of the tetrapeptide Gly-Asp(Ac)-Ser-Gly showed that
it contained no 1 8 0 . Thus it appears that ring structures involving serine and a neighboring aspartic acid are not involved in the active site.
J. I. Harris, Cambridge (England), compared some aspects of
the structure and mode of action of yeast and muscle glyceraldehyde-3-phosphate dehydrogenases (GAPDH). lnactivation of GAPDH by iodosobenzoate is due to formation
of a n intra-chain S - S bridge between two cysteines in the
“active-center” peptide. Yeast alcohol dehydrogenase contains four identical polypeptide chains each with a molecular
weight of 36000. Treatment of the enzyme with [1-14C]iodoacetic acid leads to complete loss of its activity, and the resulting S-carboxymethylcysteines occur in the same sequence
of amino acids in the enzyme protein. Some peptide sequences
in dehydrogenases are the same as some in haemoglobin.
M. F. Perutz, Cambridge (England), described the isolation of
a new form of reduced haemoglobin from horse which, when
subjected to two-dimensional X-ray crystallographic analysis, showed an increase of 7 8, in the distance between its
reactive SH groups (loaded with Hg) compared to the oxidized form. Hence the difference between horse oxyhaemoglobin and human reduced haemoglobin is not a species difference but is due to a large change in the shape of the molecule on uptake of oxygen. In a short paper, D. Lahie, Paris
(France), described a new normal human haemoglobin, haemoglobin A4.
In the colloquium on the biochemistry of chloroplasts, the
isolation of these particles in mixtures of hexane and carbon
tetrachloride was described by R . Leech, London (England).
High-soeed centrifugation between sucrose densities of 1.29
and 1.36 gave particles which wei’e morphologically closer to
those in the leaf than chloroplasts isolated by aqueous methods. However, some lipids, e.g. carotenoids and plastoquinones, had been removed; this presumably accounts for the
fact that these particles did not give the Hill reaction.
[VB 814/143 I€]
G er man version: Aneew. Chem. 76, 503 (1964)
Reactions of Compounds with Electropositive
K . Dehrzicke [I], Stuttgart (Germany)
Recrrfiows with CIF: SbClj reacts with CIF at 5 “C to form
SbC14F. Infrared and Raman spectra show that the compound
occurs undissociated as trigonal bipyramids in the molten
state and as ions [SbC14]’+ F- i n the solid state [Z]. The
force constant of [SbCld]’ corresponds with that of the isoelectronic SnC14. - AsC13 reacts with CIF as follows:
2 AsCI,
+ 6 CIF = [AsCl~]+[AsF61--i- 4 C11.
[I] In collaboration with K.-U. Meyer, .I. Weidleifz. J . Striihle,
and U . Miiller.
[ 2 ] Cf.L . Koldiri, 2. anorg. sllg. Chem. 289, 128 (1957).
Angew. Cliem. iniernai. Edit.
Vol. 3 (1964) 1 No. 6
Без категории
Размер файла
235 Кб
societies, federation, biochemical, european
Пожаловаться на содержимое документа