BIOINORGANIC

CHEMISTRY

5,359-360(1976)

359

SHORT COMMIJNICATIOlW On the Question of Phosphate Complexes of Osmium Tetroxide: Kinetics of Reactions with Nuckotides and Dinucleoside Monophosphates ROBERT L. CLARK and E. J_ BEHRMAN* Department ofBiochemistry, The Ohio State

University,

Columbus,

Ohio 43210

Konishevskaya et al. [I] observed that phosphate ions increased the rate of the reaction between hydrazine and vanadate ions catalyzed by osmium tetroxide. They claimed that phosphate ions form a 1:l complex with osmium tetroxide, & = 250 + 60. We were concerned with this report because of our interest 12-41 in the reaction between osmium tetroxide and the olefinic group of various nucleic acid derivatives which contain ionized phosphate groups and also because we have generally used phosphate buffers in our kinetic work. Table 1 summarizes our present results. The data show that sodium phosphate produces moderate rate increases in the reaction between the osmium tetroxide-pyridine system and the olefinic group in thymine derivatives in agreement with the data of Konishevskaya et al. [ 11 on the hydrazine-vanadate system. We are in TABLE 1 Rate Data for the Reaction of Thymine Derivatives with Osmium TetroxideQ

Substrate 5’-dTMP 5’-dTMP 5’-dTMP 5’-dTMP 5’-dTMP 3’-dTMP dApdT dTpdA

Phosphate (M)

0.1 0.2 0.1 0.025 0.025 0.1 0.1 0.1

Additions

Total p(M)

0.2 M NaCl

0.21

0.15 M NaCl -

0.41 0.41

0.05 0.21 0.21 0.21 0.21

kobs, M-’

miri’

18.1 t 0.5 20 20-6 16.4 18.5 19-S 25.4 5 0.5 22.9 + O-6

%eneral conditions: sodium phosphate buffer, pH 7,25”, [pyridine] = 0.16 M, [OsO, ] = 3.44 X IO-’ to 3.49 X 10e3 hi; [substrate] = 1.74 X l@ 3 to 8.6 X 10e3 M. The reactions were followed at 360 nm (product formation) as previously described under pseudo-fitor pseudosecond-order conditions. The rate law is: v = k,bs[OsO, ] [S] . See Refs. 2 and 3. Abbreviations: S’-dTMP is a’-deoxythymidine S’phosphate; 3’4ThIP is 2’deoxythymidine

3’-phosphate; dApdT is Z’-deoxyadenylyl(3 - S)Z’-deoxythymidine;

dTpdA is 2’-deoxythymidylyl(3’-

5’)2’deoxyadenosine.

*Author to whom correspondence should be addressed. 0 American Elsevier Publishing Company, Inc., 1976

:

360

R. L. CLARK AND E. J. BEHRMAN

disagreement with their interpretation, however, since our data suggest that the rate increase, in our system at Ieast, is due to an ionic strength effect and not to a specific complex_ Konishevskaya et al. [ I] reported no ionic strength controis. A replot of their data shows an approximately linear relationship between the rate of the reaction and the square root of the ionic strength [S] _ Table 1 also reports data which show that at constant ionic strength the rates of reaction of the dinucleoside monophosphates, dApdT and dTpdA, are significantly greater than those of 5’- or 3’-dTMP_ Since an adenosine residue is not oxidized at a significant rate by osmium tetroxide [ 21, we view these results as a possible indication of a neighboring group ligand effect of the adenosine residue. We are in agreement with Steinschneider and Leshem ]6] that nearest neighbor reactivity effects are an important area for future work in nucleic acid chemistry_ We

thank the iVIH for support,

GM-20375

REFERENCES 1. G. A. Kouishevskaya,V. F_ Romsnov, and K. B. Yatsimirskii,Russ_ J_ Inorg_ Chem. 18,

243 (1973); Zh. Neorg. Khim 18,462 (1973). L R Subbaraman,J. Subbaraman,and E. 3. Behrman,Bioinorg. Chem- 1,35 (1971). R L Clarkand E J. Behrman,inorg. Chem 14,142S (1975). F. B_Daniel and E. J. Behrman,J. Amer. Chem Sot 97,7352 (1975). A. A. Frost and R. C. Pearson,Kinetics and Merhanbn, 2nd Ed.. John Wrteyand Sons, Inc., New York, 1961, p_ 151_ 6. A_ Steinschneiderand B. Leshem,J. Mol. BioL 67,333 (1972).

2_ 1 4_ 5.

Received I5 July 19 75

On the question of phosphate complexes of osmium tetroxide: kinetics of reactions with nucleotides and dinucleoside monophosphates.

BIOINORGANIC CHEMISTRY 5,359-360(1976) 359 SHORT COMMIJNICATIOlW On the Question of Phosphate Complexes of Osmium Tetroxide: Kinetics of Reactions...
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