Raman spectra of fibers of DNA that have been prepared in the A, B, and C forms are presented and compared with Raman spectra of DNA and RNA in dilute solution. It is shown that the phosphate vibrations in the region 750-850 cm-' are very sensitive to the specific conformation of the phosphate group in the backbone chain and are virtually independent of all other factors. Thus, a very simple method for the determination of the specific conformation of the backbone chain of nucleic acids, at least so far as the sugar-phosphate chain is concerned, appears available. The method is applied to short oligomers and dimers of ribonucleosides. It is found that at low temperatures, at pH 7, the phosphate group goes into the geometry of the A conformation when the stacking forces between the bases are sufficiently strong.The most reliable method for the determination of the structure of nucleic acids and polynucleotide helical chains appears to be that of x-ray diffraction (1, 2). However, this method is only applicable to nucleic acids in highly concentrated fibrous form. In general, it is not applicable to dilute nucleic acid solutions, although meaningful progress in the interpretation of x-ray scattering from fairly concentrated solutions has recently been reported (3). Thus, it would seem helpful to have available a method that could be used to obtain structural information, both on fibers and on dilute solutions, where these materials naturally occur. In this paper, we wish to report the observation of several Raman bands that arise from the vibration of the sugarphosphate backbone, in both ribonucleic acids (RNA) and deoxyribonucleic acids (DNA) whose frequencies and intensities are directly related to whether or not the material is in the A, B, or C form, as designated by the x-ray crystallographers (1, 2), and are virtually independent of all other parameters, such as the base composition, the presence or absence of the 2'-hydroxyl, etc. Furthermore, these bands can be observed in single-chain structures and oligomers, so that the geometry of the phosphate group in these substances can, under favorable circumstances, be determined.Recently, work in several laboratories has shown the existence of a Raman band at about 810-814 cm-' that is always present in ribonucleic acid structures, when these structures are in an ordered or partially ordered form (4-6). This band is plainly evident in the Raman spectrum of yeast transfer RNA shown in Fig. 1, and has also been observed in ribosomal RNA (5). Upon raising the temperature of the solution, so that the secondary structure vanishes, this band at 814 cm-' inevitably vanishes (4, 5). Since this band is completely independent of base composition and is present in all ordered ribo-structures, it may be due to the sugarphosphate diestersymmetric (4, 5) stretch or antisymmetric (6) stretch. The band at 814 cm-' is highly polarized, so that the former assignment seems somewhat more reasonable. Recent work in this laboratory (4) has shown that in aqueous solution, deox...

The Raman spectra of the double helical complexes of poly C–poly G and poly I–poly C at neutral pH are presented and compared with the spectra of the constituent homopolymers. When a completely double‐helical structure is formed in solution a strong sharp band at 810–814 cm−1 appears which has previously been shown to be due to the A‐type conformation of the sugar–phosphate backbone chain. By taking the ratio of the intensity of the 810–814 cm−1 band to the intensity of the 1090–1100 cm−1 phosphate vibration, one can obtain an estimate of the fraction of the backbone chain in the A‐type conformation for both double‐stranded helices and self‐stacked single chains. This type of information can apparently only be obtained by Raman spectroscopy. In addition, other significant changes in Raman intensities and frequencies have been observed and tabulated: (1) the Raman intensity of certain of the ring vibrations of guanine and hypoxanthine bases decrease as these bases become increasingly stacked (Raman hypochromism), (2) the Raman band at 1464 cm−1 in poly I is asigned to the amide II band of the cis‐amide group of the hypoxanthine base. It shifts in frequency upon base pairing to 1484 cm−1, thus permitting the determination of the fraction of I–C pairs formed.

Over the last 2 decades assay technology originating in the laboratory has been adapted for the special situation of in vitro blood glucose monitoring in the home, at work or play, or at the bedside. The availability of blood glucose monitoring devices has had a significant impact on the treatment of diabetes, especially with respect to involving the patients in their treatment. The unique requirements of this type of testing have led to novel developments in sample acquisition techniques, analyte detection, measurement techniques, and error detection. The performance of these in vitro devices in terms of accuracy and imprecision is largely dependent on factors that contribute to variation in response that are related to testing with blood samples outside of the laboratory. These factors include, for example, variations in environmental conditions, the variability of hematocrit and oxygen concentrations of the blood, and the fact that the blood is used undiluted. Therefore, the technologies used have been selected, developed, optimized, and calibrated to minimize the impact of these factors. The technologies also must be capable of providing accurate, reproducible results over the large range of clinical interest from the hypoglycemic range to glucose concentrations 10 to 15 to 20 times greater. However, when selecting a technology there are invariably some trade-offs to consider. Thus, the products must be optimized to balance performance, reliability, and cost. Examples are discussed.

A variant creatine kinase (CK) isoenzyme was identified in the sera of some patients who had advanced adenocarcinoma of the breast, stomach, and large intestine. A similar variant isoenzyme, together with a high concentration of CK-BB isoenzyme, was identified in some breast tumor cytosols. The variant creatine kinase activity in both sera and tumor cytosols was unaffected by antibodies specific for both the CK-M and DK-B subunits. This indicates that DK-MB isoenzyme determinations are currently best performed by electrophoretic rather than immunologic technics.

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