PHOTOCHEMISTRY OF DNA CONTAINING IODINATED CYTOSINE*

Abstract— –Irradiation at 313 nm of compounds containing iodinated cytosine moieties results in the photolysis of iodine. Photolysis occurs with a quantum yield of 0·0224·024 for 5-iododeoxycytidine and 5-iododeoxycytidine monophosphate, and 0·004–0·008 for iodinated DNA as well as for iodinated polycytidylate. Photodegradation of the cytosine moiety occurs when air is present during irradiation, presumably due to the reaction of oxygen with the cytosyl radical formed when iodine is lost. This oxygen promoted photodegradation destroys the cytosine chromophore and is complete in the monomers but occurs to only a limited extent in the polymers. In the absence of oxygen or in the presence of ethanol, photodegradation is prevented and the loss of iodine leads exclusively to the formation of the cytosine chromophore. In DNA, the loss of iodine is accompanied by the formation of sugar damage and/or chain breaks. As measured by sedimentation in alkaline sucrose gradients, approximately one break is made for every six iodinqs lost in denatured DNA. The frequency of chain breakage per iodine photolyzed is reduced 2-fold in renatured DNA. Analysis in neutral gradients suggests that half of the breaks observed in alkali are alkali-labile bonds. Both ethanol and cysteamine reduce the number of chain breaks observed in alkali by ˜ 3-fold.     

On the formation of artefact peaks in linked scans of the magnet and electric sector fields in a mass spectrometer

The apperrance of peaks at non-integral masses in linked scans, where the ratio B/E is kept constant, is shown to be caused by fragmentations of metastable ions occuring in the region between the magnetic and electric sectors. A formula is given for calculating the mass of the parent metastable ion and that of its daughter ion.     

Determination of lead in atmospheric particulates by flameless atomic absorption spectrometry with a graphite tube

A procedure for the determination of atmospheric particulate lead by flameless atomic absorption spectrometry is described. Aerosols are collected on 10-cm Whatman 41 filters with high-volume pumps. The lead is removed from a one-eighth sector of the filter by two ultrasonic treatments in 0.1 M nitric acid for 10 and 5 min, respectively. Investigations, including comparison with samples pre-ashed at low temperature, indicated that the lead was completely recovered. Routinely 20-μ1 amounts of the solution are injected into a graphite tube and the % absorption at 283.3 nm is measured. The elements normally encountered in atmospheric aerosols do not interfere. The sensitivity for 24-h samples is 0.01 μg m^?3 of air. Sampling time can be reduced to a few minutes in urban air when a larger segment of the filter is used and a larger volume is injected. The reproducibility of the complete procedure is 3% for a typical lead concentration of 0.35 μg m^?3. The method was applied to short-period variations of the lead concentration in urban air.     

Selective ther cleavage in the aporphine series. Conversion of (S)-bulbocapnine into (S)-corytuberine and (S)-corydine methyl ether.

Bulbocapnine methyl ether ( 2 ), on treatment with boron halides, affords the aporphine-1,2-diol ( 3 ), the novel aporphines 5 and 6 or the phenanthrene derivative 11 depending on the reaction conditions. 3 can be further transformed into corydine methyl ether ( 4 ); 6 has been converted to corytuberine ( 8 ). Similarly, dehydrobulbocapnine methyl ether 9 was converted to 10 .     

Molecular emission cavity analysis : Part VII. The determination of cadmium

Cadmium salts give an intense cadmium atomic emission in the MECA cavity in a hydrogen-nitrogen-air flame. When a carbon or stainless steel cavity is used, 10–120 ng of cadmium in 5-μl samples can be determined. In the presence of sulphuric acid, anionic interferences are removed. Of the cations, only Fe(III), Cr(III), Mg and Sn(II) interfere seriously.     

On the Relation Between Gegenbauer Polynomials and the Ferrers Function of the First Kind

Analysis Mathematica - Using the direct relation between the Gegenbauer polynomials $$C_n^\lambda(x)$$ and the Ferrers function of the first kind $${\rm{P}}_\nu^\mu(x)$$ , we compute interrelations...     

Pointwise and uniform error estimates associated with Abel-Whittaker interpolation series and its dual

BIT Numerical Mathematics - Abel-Whittaker series (1934) is viewed as a two-point Taylor series. It solves the interpolation problem $$f^{(2n)}(1) =a_n$$ , $$f^{(2n+1)}(0) =b_n,\,n\ge 0,$$ for an...     

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Evaluation of new single crystal piezoelectric materials for surface acoustic-wave applications

Surface acoustic waves (SAW), or Rayleigh waves, bound to the surfaces of piezoelectric materials are becoming rapidly significant in electronic device applications, particularly as VHF-UHF frequency filters and versatile time-domain processors. The majority of available devices utilize either signle crystalline quartz or lithium niobate as the piezoelectric medium. This paper describes briefly the growth and critical evaluation of SAW impedance and propagation properties for certain new single crystal piezoelectric materials. Crystals discussed are Czochralski-grown bismuth germanium oxide, films of zinc oxide and aluminum nitride both epitaxially grown on single crystal sapphire, and flux-grown beryllium oxide. It is concluded that bismuth germanium oxide may prove an important cost-effective alternative to both quartz and lithium niobate, and that either zinc oxide or aluminum nitride is destined to prove invaluable in the realization of monolithic circuits such as programmable tapped delay lines, in which SAW will be interfaced with metal-oxide semiconductor (large scale integrated) technology, and active SAW elements employing functional integration.