The effect of superhelicity on the interaction of histone f1 with closed circular duplex DNA.

A set of covalently closed circular duplex simian virus 40 DNA preparations of varying superhelical densities was prepared by closure of nicked duplex DNA with polynucleotide ligase in the presence of varying amounts of ethidium. The resulting molecules were tested for complex formation with the lysine-rich histone f1. The results confirmed earlier experiments in demonstrating that f1 histone reacts preferentially with superhelical DNA compared to relaxed circular DNA. Furthermore, the extent of the reaction is demonstrated to depend on the superhelical density. At the relatively low ratios of histone to DNA used in these experiments, the product of the interaction of f1 histone with superhelical DNA does not precipitate. At higher ratios of histone to DNA, an insoluble aggregate is formed.     

The use of several energy-coupling reactions in characterizing mutants of Escherichia coli K12 defective in oxidative phosphorylation.

Oxidative phosphorylation, ATP-32Pi exchange, ATP-dependent quenching of acridine-dye fluorescence, ATP-dependent transhydrogenase and ATP-dependent transport of thiomethyl beta-D-galactoside are shown to be experimentally equivalent tools to study the functional state of the ATPase complex in Escherichia coli wild-type and mutant strains defective in oxidative phosphorylation. According to these criteria ten mutants in the ATPase complex were classified having lesions in the unc A,B region of the chromosome. The first mutant type lacks ATPase activity, but the membrane-integrated part of the complex remains functional (class I). The second mutant type lacks a functional membrane-integrated part, but retains ATPase activity (class II). The third mutant type is shown to be defective in both parts of the ATPase complex (class III).     

Detection of BrdUrd incorporation in mammalian chromosomes by a BrdUrd antibody

Summary A bromodeoxyuridine antibody staining technique (BAT) was applied for the analysis of human chromosomes of different chromosomal band resolution. For this purpose lymphocyte cultures were synchronized and labeled with bromodeoxyuridine during the second half of the S-phase. Generally BAT was found comparable to GTG banding though some prominent GTG bands and the constitutive heterochromatin exhibit less intense staining with this technique.     

Correlation of <Emphasis Type="Italic">trans</Emphasis>-Lycopene Measurements by the HPLC Method with the Optothermal and Photoacoustic Signals and the Color Readings of Fresh Tomato Homogenates

The trans-lycopene content of fresh tomato homogenates was assessed by means of the laser photoacoustic spectroscopy, the laser optothermal window, micro-Raman spectroscopy, and colorimetry; none of these methods require the extraction from the product matrix prior to the analysis. The wet chemistry method (high-performance liquid chromatography) was used as the absolute quantitative method. Analytical figures of merit for all methods were compared statistically; best linear correlation was achieved for the chromaticity index a* and chroma C*.     

Sedimentation coefficients of self-associating species: I. Basic theory

Under the same solution conditions, the apparent weight average sedimentation coefficient, s_wa, and some quantities obtained from it can be combined with the equilibrium constant or constants, K_i, and the monomer concentration, c_I, obtained from sedimentation equilibrium, light scattering or osmotic pressure experiments on the same self-associating solute, so that the individual sedimentation coefficients, s_i, of the self-associating species, and also the hydrodynamic concentration dependence parameter,g or $\text{g}$, can be evaluated. Using two different models for the hydrodynamic concentration parameter, four different methods are presented for the evaluation of the s_i's. Methods for evaluating g or $\text{g}$, once the s_i's are known, are presented. A method for obtaining the number average sedimentation coefficient, s_N, and its application to self-associations is presented. Methods are shown for the evaluation of Z average properties, x_zc, as well as number average properties,x_Nc, of a self-associating solute from its weight average properties, x_wc.