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Highly purified nicking-closing enzyme from mouse cells in 20-fold enzyme/substrate excess converts closed circular native PM2, ColEl, and Minicol DNA into limit product sets of DNAs. Each set has a mean degree of supercoiling of approximately zero. The individual species in the sets differ by Ar = i1, i42, etc., and the relative masses fit a Boltzmann distribution. It was also demonstrated that "nonsupercoiled" closed circular duplex molecules serve as substrates for the nicking-closing enzyme, and that a distribution of topological isomers is generated. Polynucleotide ligase, acting on nicked circular DNA, forms under the same conditions, the same set of closed DNAs. The latter enzyme freezes the population into sets of molecules otherwise in configurational equilibrium in solution.Nicking-closing (N-C) activities that alter the topological winding number (a) of closed circular DNA occur widely in nature (1-5). The topological winding number is the number of revolutions that one strand makes about the other if the molecule is constrained to lie in a plane. The activities have been demonstrated to be enzymatic with proteins from Escherichia coli (6), mouse (7), and human (8) cells in culture. The N-C enzyme from mouse LA9 cell nuclei, purified to homogeneity in good yield, is a major constituent of chromatin and accounts for about 1% of the total protein (H-P.Vosberg and J. Vinograd, unpublished work). It is similar to other eukaryotic N-C enzymes in its ability to relax both positive and negative superhelical turns. A probable in vivo role for the enzyme is to provide the transient swivels required for DNA replication. Such swivels may also be required in transcription, and in the condensation and decondensation of chromatin.In this study we have examined the limit product of the action of N-C enzyme on several closed circular DNAs by gel electrophoresis. Under appropriate analytical conditions, the limit product separates into a set of species differing in topological winding number. Individual species, isolated from the set, regenerate the original distribution upon incubation with the N-C enzyme. We view the foregoing as the consequence of four necessary events: nicking of the DNA, relaxation, random rotation about the swivel, and closure (Fig. 1). A set of species is also found when E. colh polynucleotide ligase is used to close a nicked circular DNA (9, 10). It is shown here that distribution of products obtained with ligase is indistinguishable from that obtained with N-C enzyme when the incubation conditions are the same for both reactions.The relative masses of the species, when plotted against a, fall on a Gaussian curve. Such a curve is anticipated for a Boltzmann distribution, when the energy of supercoiling is Abbreviations: N-C, nicking-closing; EtdBr, ethidium bromide.proportional to the square (11) of the degree of supercoiling. The similarity of the products obtained with two different enzyme systems and the further similarities of the values of the free energy of supercoiling obtained...

The executive functions (including response inhibition, memory updating, and task switching) appear to form the core of higher-order cognitive processes in humans. Relatively little research has been devoted to the role of the executive functions in emotional and motivational processes. The current article surveys evidence on the contributions of individual differences in executive functioning to emotion and emotion regulation in adults. The findings reveal that cognitive ability helps to shape human emotional life and raise new questions about how and why this is so.

Abstract. Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using a long-path absorption photometer (LPAP). A Na 2 CO 3 -coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 1-min averages, with an overall uncertainty of ± (1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ± (8 × 10 −8 + 0.15 F HONO ) mol m −2 h −1 , with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10 −6 moles m −2 h −1 . The HONO flux reached a maximal mean of ∼ 0.7 × 10 −6 moles m −2 h −1 around solar noon, contributing a major fraction to the HONO source strength required to sustain the observed ambient concentration of ∼ 70 pptv. There were no significant correlations between [NO x ] and daytime HONO flux and between J NO 2 × [NO 2 ] and HONO flux, suggesting that NO x was not an important precursor responsible for HONO daytime production on the forest canopy surface in this low-NO x rural environment. Evidence supports the hypothesis that photolysis of HNO 3 deposited on the forest canopy surface is a major daytime HONO source.

Nerve entrapment syndromes are common in the general population, and are managed by a wide variety of medical and surgical specialists. A thorough understanding of the pathophysiology of nerve compression and appropriate clinical workup are critical in the overall management of these conditions. There remain several topics of controversy regarding the surgical management of nerve entrapment syndromes, including multiple points of nerve compression, carpal tunnel release under local anesthesia, open versus endoscopic decompression surgery, the "best" operation for primary cubital tunnel surgery, and revision decompression surgery. This article attempts to provide a concise summary of the advances in the basic and clinical science of peripheral nerve entrapment.

Therapeutic, I.

Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using an optical fiber spectrometer with a 1-m long path flow cell. A Na₂CO₃-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 2-min averages, with an overall uncertainty of &plusmn;(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within &plusmn;(8 &times; 10⁻⁸ + 0.15 <i>F</i>_HONO) mol m⁻² h⁻¹, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 &times; 10⁻⁶ moles m⁻² h⁻¹. The HONO flux reached a maximum mean of ~0.7 &times; 10⁻⁶ moles m⁻² h⁻¹ around solar noon, contributing a major fraction (~60%) to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There was no significant correlation between NO_x and daytime HONO flux, suggesting that NO_x was not an important precursor responsible for HONO daytime production on the forest canopy surface in the low-NO_x rural environment. Evidence suggests that photolysis of HNO₃ deposited on the forest canopy surface is a major daytime HONO source