choline. Our findings could also explain why, in shock lung syndrome, patients do not always respond to therapy with certain vasodilator drugs (3). Irrespective of the exact mechanism, selective removal of endothelium from intrapulmonary arteries can transform two important circulating dilator agents into pulmonary vasoconstrictors. It is thus conceivable that damage in vivo to intrapulmonary arterial and arteriolar en- dothelial cells or destruction of pulmo- nary arterial endothelial cells by a num- ber of agencies acting alone or in concert (for example, chronic hypoxia, release of hydrolytic enzymes, leukocyte platelet- endothelial cell interactions resulting in release of lysosomal enzymes, microag- gregation of formed elements adjacent to these endothelial cells) may represent the major pathway in producing pulmo- nary hypertension or shock lung. Our data may also explain why, in numerous studies on isolated pulmonary blood vessels-which are often trauma- tized in preparation-acetylcholine and certain other so-called vasodilators will produce contraction rather than dilation of these vessels (6). NARESH CHAND BURTON M. ALTURA Department of Physiology, State University of New York, Downstate Medical Center, Brooklyn 11203 References and Notes 1. R. F. Furchgott and J. V. Zawadzki, Pharma- cologist 21, 271 (1979); Fed. Proc. Fed. Am. Soc. Exp. Biol. 39, 581 (1980); Nature (London) 288, 373 (1980); , P. D. Cherry, in Mecha- nisms of Vasodilatation, P. M. Vanhoutte and I. Leusen, Eds. (Raven, New York, in press), vol. 2. 2. J. B. West, Pulmonary Pathophysiology-The Essentials (Williams & Wilkins, Baltimore, 1977); J. K. Perloff, in Pulmonary Vascular Disease, K. M. Moser, Ed. (Dekker, New York, 1979), p. 489; M. Voelkel and J. T. Reeves, in ibid., p. 573. 3. A. P. Thal, E. B. Brown, Jr., A. S. Hermreck, H. M. Bell, Shock. A Physiologic Basis for Treatment (Year Book, Chicago, 1971); J. W. Wilson, in The Cell in Shock (Upjohn, Kalama- zoo, Mich., 1974), p. 39; B. J. Pardy and H. A. F. Dudley, Surg. Gynecol. Obstet. 144, 259 (1977). 4. N. Chand and B. M. Altura, J. AppI. Physiol. 49, 1016 (1980); Prostagland. Med. 5, 59 (1980); B. M. Altura and N. Chand, Br. J. Pharmacol., in press. 5. B. M. Altura and B. T. Altura, Am. J. Physiol. 219, 1698 (1970). 6. E. H. Bergofsky, in Pulmonary Vascular Dis- ease, K. M. Moser, Ed. (Dekker, New York, 1979), p. 233; P. M. Vanhoutte, in Microcircula- tion, G. Kaley and B. M. Altura, Eds. (Universi- ty Park Press, Baltimore, 1978), vol. 2, p. 181. 7. Intrapulmonary arteries were fixed in 2 percent glutaraldehyde and 0.1M potassium phosphate (pH 7.4) for 60 minutes at 4C, postfixed in I percent 0,04 and 0.1M potassium phosphate, dehydrated in a graded ethanol series, and em- bedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate. These were then examined and photographed in a JEOL IOOC electron microscope. 8. Supported in part by PHS research grants NHLBI 18002, NHLBI 18015. and DA 02339 (to B.M.A.). We thank G. K. Ojakian and D. Herz- linger for performing the electron microscopy. Requests for reprints should be addressed to B.M.A. 16 April 1981; revised 4 June 1981 SCIENCE, VOL. 213, 18 SEPTEMBER 1981 Chiral Recognition by Nucleosides and Nucleotides: Resolution of Helicenes by High-Performance Liquid Chromatography Abstract. Chiral recognition by nucleosides and nucleotides coated on silica gel was studied by high-performance liquid chromatography. Helicenes, which are chiral polyaromatic hydrocarbons, were used as probes. Stereoselectivity was detected when the nucleobase was a purine (adenosine, deoxyadenosine, adenosine 3'-monophosphate, adenosine S'-monophosphate, adenosine 3',5'-monophosphate, and guanosine), but was not detected with the pyrimidine derivative uridine. For a given nucleobase (adenine), all changes in the ribose moiety affected the resolution factors, which ranged between 1.03 and 1.074. These results might be relevant to the enantioselectivity of carcinogenic metabolites of polyaromatic hydrocarbons. We recently described enantioselec- tive interactions of riboflavin with chiral ortho-condensed polyaromatic hydro- carbons as manifested in resolutions of optical isomers by high-performance liq- uid chromatography (HPLC) (1). We now report a similar study with nucleo- sides and nucleotides coated on the col- umn packing material. As in the ribofla- vin study (1), helicenes, which have a helical shape due to overcrowding, were the compounds resolved. Although heli- cenes do not occur in nature, the results may be of interest for probing the capaci- ty of nucleic acid building blocks for chiral differentiation. P(+)-Hexahelicene M(-)-Hexahelicene The compounds tested were 1, adeno- sine; 2, deoxyadenosine; 3, adenosine 3'- monophosphate (3'-AMP); 4, adenosine 5'-monophosphate (5'-AMP); 5, adeno- sine 3',5'-monophosphate (cyclic AMP); 6, guanosine; and 7, uridine. Purines and pyrimidines form complexes with poly- Time (minutes) aromatic hydrocarbons. Combination of a purine or pyrimidine with a chiral sub- stituent such as ribose could lead to chiral differentiation of optically active polyaromatic hydrocarbons, in analogy NO2 NO2 NH2 NO2 NO2 WCN N N HOH2C H-C-CH3 COOH HO OH R(-)-TAPA Adenosine with the behavior of R(-)-2-(2,4,5,7- tetranitrofluorylidene-9-aminooxy)pro- pionic acid (TAPA) (2) and of riboflavin (1). The molecular interaction of nucleo- bases with polyaromatic hydrocarbons differs from that of TAPA and riboflavin, since for the nucleobases the contribu- tion of charge transfer is considered to be of little importance as compared with van der Waals forces (3). The nucleosides and nucleotides were coated on 5-,um silica gel (Lichrosorb Si 100, Merck, Darmstadt, Germany) and HPLC columns were prepared by slurry packing. The amount of coated material, determined by elementary analysis, var- Fig. 1. Resolution of the opti- cal isomers of [101- to [13]- carbohelicenes on adenosine- coated silica gel. The number in brackets indicates the num- ber of rings in an individual helicene. The chromatograph- ic system consisted of a Wa- ters 6000A pump, a Reodyne 7120 injector with a 20-,Ll loop, and an LDC ultraviolet moni- tor set at 254 nm. The column was 20 by 0.46 cm (inside di- ameter). The eluant was CH2Cl2 and n-hexane (1:9); the flow rate was I ml/min; , and the temperature 230 to 20 25'C. The elution curves cor- respond to (A) [101-helicene enriched in the M(-)isomer, and (B) [11]-, (C)[12]-, and (D) [131-helicenes. 0036-8075/81/0918-1379$01.00/0 Copyright © 1981 AAAS 1379 on March 28, 2016 Downloaded from on March 28, 2016 Downloaded from on March 28, 2016 Downloaded from