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COMMUNICATIONS TO
free chlorine recovered from the liquid nitrogen trap agreed, within experimental error, with the diboron tetrachloride produced. 2BC& +BtClr
+ C12
Only trace amounts, if any, of lower chlorides of boron were observed. Various parameters which might increase the concentration of active species and a t the same time inhibit recombination of chlorine with diboron tetrachloride are under investigation. The attractiveness of this procedure lies in its simplicity and probable adaptability to other systems.
THE
EDITOR
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TABLE I BICARBOSATE REQUIREMENT FOR FATTY ACID BIOSYXTHESIS KHCOa added (&moles) 0 1.0 2.0 4 . 0 5.0 Acetyl CoA incorporated 1 . 0 8 . 0 1 9 . 0 25.0 24 . 0 into fatty acids (mpmoles) Each experimental tube contained the following reagents (in a final volume of 0.50 ml.): 50 &molesof potassium phosphate buffer (pH 6.5); 1.0 pmole of ATP; 0.3 pmole of MnC12; 0.05 pmole of T P N H ; and 50 mmoles of acetyl-lCI4 c o 4 . The reaction was started by addition of the ~ ~mg. : R1,and 0.4 mg. Rzg. All purified liver e n z y r n e ~ ~0.7 samples were incubated five minutes a t 38".
UNIVERSITY OF CALIFORSIA RADIATION LABORATORY JACK W. FRAZERformate, acetate, malonate, a-ketoglutarate, isoLIVERMORE, CALIFORNIA R. T. HOLZMANNcitrate or succinate. This absolute requirement RECEIVED APRIL 19, 1958 for HC03- applies to the system a t all stages of
purification4 providing that (a) HC03- is removed from enzyme and reagent solutions, and (b) REQUIREMENT FOR BICARBONATE IN FATTY ACID systems which generate HC03- are eliminated. SYNTHESIS' Radio-labelled HC03- is not incorporated into Sir: U'hile studying a highly purified enzyme system2 long-chain fatty acid. Hence HC03- cannot be from avian liver which catalyzes the synthesis of considered a substrate for fatty acid synthesis. palmitic acid from acetyl CoA in the presence of il'7epostulate a catalytic role for this component. The oxidation of T P N H in the complete system hln++, ,4TP3 and T P N H we have observed an provides an alternative measure of biosynthesis.2 absolute requirement for bicarbonate ion (or its equilibrium forms). Table I shows the character- The absolute requirement for HC03- is also readily istics of this requirement. The half-maximal rate demonstrable in this spectrophotometric assay (cf. Fig. I ) . of fatty acid synthesis is attained a t a HC0,The requirement for HC03-, as well as ATP,2 concentration of less than 2 X l o p 3 -11. HC03- is not replaceable by phosphate, sulfate, chloride, have suggested to us the possible participation of still another cofactor. I n this regard it is signifid. .. cant that one of the purified enzyme fractions conn !! " tains a considerable concentration of proteinNO' HCOg bound biotin.?
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(4) S. J . Wakil, J . \I,, Porter and D. 11. Gibson, Hiochim. Biophys. A c f a , 24, 453 (1957); J. \V. Porter, S. J . U'akil, A . Tietz, h l . I. Jacob and D. M . Gibson, i b i d . , 26, 35 (1957). (5) This work was carried o u t during the tenure of an Established Investigatorship of the American Heart Association, Inc. (6) Postdoctoral trainee of the Institute f o r Enzyme Research, University of Wisconsin.
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INSTITUTE FOR EXZYME RESEARCH DAVIDM. GIBSOX5 UNIVERSITY OF WISCONSIN EDWARD B. TITCHENER~ MADISOX, WISCOXSIX SALIHJ. \VAKIL RECEIVED FEBRUARY 14, 1958
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THE PRESENCE OF NS+ AND N1+ IN THE MASS SPECTRA OF MOLECULAR NITROGEN
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We have used two G O O sector instruments equipped with viscous and molecular leaks to study the mass spectra of purified tank nitrogen' a t high Fig. 1.-Oxidation of TPXH with and without added source pressures. ,2 42+ and a 5G+ ion current HCOa-: the conditions for these experiments are identical were observed in addition to those currents norto those in Table I except that 32 mpmoles of acet1~l-l-C'~ mally produced by the ionization and fragmentation CoA was added in each cuvette; 4.0 pmoles of K H C 0 3 was of nitrogen. At first, i t was suspected that the two added as indicated. In the complete system 17 mpmoles unusual currents resulted from an increase in the of acetyl CoA was incorporated into fatty acids, while background due to the high operating pressures. there was no incorporation in the system without HC03-. High purity argon was used to check this suspicion. (1) This investigation has been supported by a research grant, I t was found that the small 42+ and 56' backMN-3, from the American Cancer Society; by a research grant Hground ion currents remained constant when argon 2236(C2) and postdoctoral training grant, HTS-5006(CS), from the was run a t the same pressures as those used to National Heart Institute of the National Institutes of Health, Public determine the nitrogen spectra. We also found Health Service; and Contract Nonr-1202 from the Office of Naval Research. that nitrogen prepared by the hypobromite oxida( 2 ) S. J. Wakil. E. B.Titchener and D. M. Gibson, Biochim. Biophys. tion of reagent grade ("&SO4 gave the same 42+ Acta, in press.
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(3) T h e following abbreviations are used: ATP, adenosine triphosphate; and T P N H , reduced triphosphopyridine nucleotide.
(1) Prepurified grade obtained f r o m the Matheson C o , Juliet, Illinois.
