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Application of Electron Paramagnetic Resonance Spectroscopy in Studies on Oxidizing Enzymes.

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The cyclic N- hydroxylaminoacetal of 5-hydroxypentanal(II)
is remarkably stable. On standing for several months at room
temperature no change could be observed. However, on
/\
()-ox
-
CHjNHOH
A
()-NC&
AH
0
0)
(ID
/\
(O$=Z-CHi
(111)
distillation in Y ~ C U Oa considerable amount (ca. 40%) isornerized to the tautomeric N-oxide of 5-hydroxy-I-(N-methyl-
imino)pentane (111) (b.p. 15O0C/O.3mm.; nL3 = 1.4858). The
structure of (111) was elucidated by analysis and infrared
spectroscopy (C=N: 6.0 p; N + 0: 6.6 p). The physical
data for (111) are in agreement with those of its higher
homologs [3].
[Z 274/104 IEI
Received, May 10th. 1962
[I]E. Bamberger, Ber. dtsch. chem. Ges. 33,941(1900); H. Hellmann and K . Teichmann, Chem. Ber. 89, 1134 (1956).
[2] G. A. Snow, J. chem. SOC. (London) 2588 (1954).
[3] A. A. Sayigh and H . Ulrich, unpublished.
CONFERENCE REPORTS
Luminescence Amplification and Extinction
by Electric Fields
H. E. Gumlich, Berlin-Dahlem (Germany) and Newark, Del.
(USA)
The amplification and extinction of the luminescence of
powdered manganese-activated ZnS- and ZnS-CdS phosphors by electric fields depends on the field strength, field
frequency, intensity and wavelength of the exciting radiation,
the emission wavelength, and the temperature. Of particular
interest are phosphors whose luminescence can also be
amplified by infrared and red light and those in which the
number of radiationless efectronic recombinations is increased
by the additional inclusion of cobalt. An investigation of these
phosphors reveals that the maximum amplification is
produced by infrared and red light of wavelength 1350 and
770 mp, respectively. The field amplification attains a
maximum for field frequency between 10 and 100 cps. If the
exciting radiation, the stimulating light and the electric field
all act simultaneously on these phosphors, then the effect of
the electric field and of the stimulating radiation is not equal
to the sum of the individual effects, i.e. the infrared amplification and the field amplification are not independent of one
another. The nature of the interaction depends on the field
strength, the field frequency and the intensity of the stimulating radiation but not, however, on the cobalt content.
The cobalt content of the phosphor does have a marked
effect on the field amplification. The luminescence amplification in its dependence on the cobalt content passes through
a maximum: low cobalt concentrations cause an amplification
greater than, and high cobalt concentrations cause an amplification smaller than is the case in the absence of cobalt.
With a cobalt addition of 10-6 parts by weight and at low
field frequencies, the electric field can effect an eighteenfold
increase in luminescence. The Iuminescence amplification
observed for powdered phosphors was compared with the
field amplification effects measured in the red bands for CdS
single crystals.
(GDCh-Ortsverband Berlin (Germany), February 20th. 19621
[VB 577122 IE]
The Chemistry of Mercaptoacrylic Acid
Derivatives
K.-D. Gimdermann, Munster (Germany)
Following a survey of a- and p-alkylmercaptoacrylic acid
derivatives [l] a new, generally applicable, method for the
preparation of a,/3-bis[alkylmercapto]acrylicacid derivatives
was presented: Mercaptalization of formylalkylmercapto-
Jd0
+ H2C-COOR
.,4
'OR
/OH
+ HC==C-COOR
I
-+
SR
,sR'
HC-CH-COOR
RS'
336
$R
+ HC-C-COOR
I
SR
kR'
(I) R=H,R'=CH&Hs
acetate fotlowed by removal of one mole of mercaptan from
the mercaptals by means of KHS04 yields esters of a,P-bis[alkylmercapto]acrylic acid.
The easily accessible a,P-bis-[benzylmercapto]acrylic acid (I)
can then be converted to 1,4-dithi-2-ene-2-carboxylic
acid as
well as to the higher melting a$-bis[methylmercapto]acrylic
acid [2] by debenzylation with sodium or lithium in Iiquid
ammonia and subsequent realkylation with 1,Z-dichloroethane or methyl iodide. Thus their steric assignment is
confirmed.
CHI
HjCS--C/
'CH2
I
H!
C-SCH?
'O/
(")
HCO
The relatively high dibenzyl formation of up to 50 % of the
theoretical amount, during the reductive debenzylation, also
supports the cis-configuration of both benzylmercapto groups
in (I); this is explained by the spatial proximity of the two
benzylmercapto groups (fixation by the double bond). The
characteristic dimerization tendency of a-alkylmercaptoacrylonitrile and ester is also found with a-alkylmercaptoacroleins; the a-methylmercaptoacrolein synthesized from
thioglycidaldehyde diethylacetal 131 by way of P-diethylamino-a-mercaptopropionaldehydediethyl acetal has. up to
the present time, only been obtained as the semicarbazone of
dimer (11).
The peculiar reactivity of a-alkylmercaptoacrylic acid derivatives is explained by the fact that thioether groups can act as
electron donors as well as acceptors [4].
[GDCh-Ortsverband Ruhr, MiiIheimlRuhr (Germany),
March 28th. 19621
[VB 578/29 IE]
[l] K. D . Gundermann and R . Huchting, Chem. Ber. 95, 632
(1962) and earlier communications.
121 K. D. Gundermannand R. Thomas, Chem. Ber. 91,1330(1958).
[3] J. B. Wright, J. Arner. chem. SOC.79. 1694 (1957).
[4] G. Cilento, Chem. Reviews 60, 147 (1960);H . C. Volger and
J. F. Arens, Rec. trav. chim. Pays-Bas 77, 1170 (1958).
Application of Electron Paramagnetic Resonance
Spectroscopy in Studies on Oxidizing Enzymes
Helmut Beinert, Madison, Wisc. (USA)
Although electron resonances (EPR) spectroscopy has many
potential applications in the study of biological problems.
One of the most serious handicaps of the method is its relative
insensitivity in aqueous media, owing to the strong background absorption of microwave energy by water. Nevertheless, recent experimental work has shown that in problems of
enzyme chemistry, EPR spectroscopy may yield answers which
cannot at present be obtained by other methods. Thus, for
example, a new group of oxidation-reduction catalysts were
discovered in beef heart mitochondria, that can only be recognized by their characteristic EPR signals [I]. Typical asymmetrie signals (g 11 = 2.00, g l = 1.94) are observed even with
samples of freshly frozen whole heart or liver and are also
Angew. Chem. internat. Edit. 1 Vol. I (1962) / No. 6
found in isolated mitochondria and submitochondrial particles obtained by sonic disintegration of mitochondria. The
signals appear when the oxidation-reduction catalysts are in
the reduced state and show some differences depending on the
reducing substrate added. When a dehydrogenase specific for
a particular substrate (e.g. succinate, DPNH) is isolated, the
signal characteristic for reduction by this substrate is found
in the isolated enzyme. Signals of the same general type have
also been found in bacteria, in xanthine oxidase from milk, aldehyde oxidase from liver, and dihydroorotic dehydrogenase.
The new catalysts are thought to be protein-bound iron
complexes, which do not involve porphorin. Chemical and
spectroscopic analyses exclude other metals. Direct evidence
that iron is responsible for the signals was obtained in
experiments with 57Fe. Kinetic studies were carried out in
which the redox state of the cytochrome components was
assessed by optical reflectance spectroscopy on the same
frozen samples, which were then subjected to EPR spectroscopy. Thus, the new catalysts and the cytochromes courd be
observed at the the same state by both methods. The rate of
reduction and reoxidation of the new catalysts did not differ
from that of the cytochromes. In addition, reduction of the
copper of cytochrome oxidase could be observed under these
conditions. It is possible to assess the state of the copper in
this enzyme during isolation procedures. A change in the
ligand environment of the copper is easily recognized. Quantitative evaluation of the spectra indicates that there may be
a pair of vicinal copper atoms in cytochrome oxidase. The
possibility of reaction of this pair of copper atoms with oxygen
forms an attractive hypothesis. Experiments with dihydroorotic dehydrogenase - again applying combined optical and
EPR spectroscopy - confirmed a previous suggestion [2]
that semiquinoid forms of flavoproteins have absorption
bands at about 600 mp and that flavoproteins are not
necessarily reduced to their leuco-forms by their substrates,
but rather to the semiquinoid level only, so that during
active catalysis one would expect turnover mainly between
oxidized and semiquinoid forms.
[Max-Planck-Institut Heidelberg (Germany),
March 26th. 19621
[VB 579/28 IE]
[I] Cf. H . Beinert and W.Lee, Biochem. Biophys. Res.Commun.
5, 40 (1961).
[2] H. Beinert, J. biol. Chemistry 225, 465 (1957).
SELECTED ABSTRACTS
Stereospecific polymerization of isoprene with calcium-zinc
alkyl and titanium salts was studied by W. Murconi, A. Muzzei, S. Cucinella, and M. De Malde. A polyisoprene with
about 70 % 1,4-trans- and 22 % 3,4-linkages is obtained with
the catalyst complex (CaH&Xa(CzH5)2yZn(C2H5)2, available
from the reaction of metallic Ca with Zn(C2Hs)z. However,
the reaction in benzene tends to be more stereospecific if
small additions of Tic14 are made. The structure of the
polymer depends to a large extent on the ratio (Ca + Zn)/Ti.
At a ratio of 0.5 or less, one obtains primarily the 1,4-truns
compound, while the 1,4-cisstructure predominates at ratios
between 0.6 and 0.9. A mixture of 1,4-cis-, 1,4-trans-, arM
3,4.isomer is obtained only after a ratio of about 2 is reached.
The activity of the catalytic system is affected by the ratio of
Ca/Zn. The best results, with regard to yield and stereospecificity, are obtained with a Ca/Zn mole ratio between 0.3
and 1.88 and a (Ca + Zn)/Ti ratio between 0.6 and 0.9. /Chim.
[Rd 129/53 IE]
e Ind. 44,121 (1962). 1 -Pf.
Thin-layer chromatographic separation methods can be scaled
up to column size by means of horizontal chromatography
in cellophane tubing. H.Dahn and H. Fuchs pressed gypsumfree adsorbents suitable for thin-layer chromatography into
a dialysis tube with the aid of a rod and carried out horizontal
chromatography using a special flow tank. About 250-300
mg. of mixture can be separated on silica gel t r aluminum
oxide columns having a length of 40 to 45 cm. and a diameter
of 3.6 cm. The zones representing different substances are
observed in visible or ultraviolet light [to which the cellophane tubing is transparent), with addition of fluorescent
substances to the column packing when necessary. If fluids of
low volatility are used, RF values obtained from the layers
can be used directly in column calculations. The zones
containing the substances may be separated simply by
cutting the chromatogram. / Helv. chim. Acta 45,261 (1962) /
-Ra.
[Rd 92/44 IE]
The synthesis of santene in a two-step reaction with an overall
yield of 40 %, has been accomplished by H. J. Ache. In the
first step, cyclopentadienylsodium was alkylated with methyl
bromide in liquid ammonia. 'This reaction is applicable for
the synthesis of mono- or di-substituted cyclopentadienes in
general and gives excellent yields. Diels-Alder addition of
eythlene to give santene (I) was achieved at 250°C and 200
atm. The reaction product thus formed also cuntained methylnorcamphene (11) and its isomers, and was separated into its
components by distillation using a spinning-band column. /
Chem. Ber. 45,503 (1962) /-Re.
[Rd 130154 IE]
Angew. Chem. internaf. Edit. 1 VoI. I (1962) I No. 6
A boron ylide (I)
bearing
,
a negative charge on the boron
atom and a positive charge on the carbon atom, is postulated
by H. Jager and G. Hesse as an intermediate in the reaction
between lithium tetrabutyl boron (11) and alkylating agents
such as benzyl chloride:
B
[(C4H9)3B-C4H9]Li@ + CsHs-CH2CI
e
+
H
+(C~H~)Z-B-C-C~H~
+ I
HB(C4Hg)z
+ C~HS-CH=CH-CHZ-C~H~ t
I
(C~H~)IB--C--C~H~
I
(W
C4H9
The existence of (I) as an intermediate is suggested especially
by the formation of octene (51.3 % yield) which, in the
opinion of the authors, is formed from (I) by anionotropic
migration of a butyl group and subsequent elimination of
HB(C4H9)2from di-(n-butyl)-4-octylboron(111). If the lithium
tetrabutyl boron is oxidized before working up and the
borate ester thus formed is hydrolyzed, a mixture of octanols
containing predominantly octan-1-01 is obtained in 9 %
yield. The rearrangement (I) + (111) is the counterpart of the
Stevens rearrangement in the chemistry of the nitrogen
[Rd 128/52 IE]
ylides. 1 Chem. Ber. 95, 345 (1962). / -Sk.
A new carbon-nitrogen compound, 3,6-dicyano-l,2,4,5-tetrazine, C4N6, has been synthesized by E. Gryskiewicz-Trochimowski and M. Bousquet. The compound (I) was obtained by
dehydration of 1,2,4,5-tetrazinedicarbonamide(11) with PzOs
at 14O-17O0C at 0.1 mm. Hg (Ar atmosphere), the reaction
product subliming off (yield 12-18 %). The compound is
CONH,
I
CONHI
CN
1
CN
unstable and can be stored in Ar for a few hours only. It
forms ruby-red prisms, which dissolve in organic solvents
(with the exception of petroleum ether), yielding strongly
colored solutions. Water and mineral acids decompose the
compound, which rapidly splits off HCN and Nz. / Compt.
Rend. hebd. Stances Acad. Sci. 253, 2992 (1961). / -Ma.
[Rd 134/58 IE]
337
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