The detection of superoxide anion from the reaction of oxyhemoglobin and phenylhydrazine using EPR spectroscopy

Summary The low temperature EPR spectrum of a quickly reacted mixture of oxyhemoglobin and phenylhydrazine was studied. With the use of a computer, the spectral contribution of methemoglobin in the region of g=2 was subtracted. The remaining spectrum was that of an axial free radical (g=2.00, g=2.06) having the magnetic parameters of superoxide anion. In the presence of superoxide dismutase, this axial radical was not seen, confirming that superoxide anion is indeed generated by the reaction.The portion of this investigation carried out at the Albert Einstein College of Medicine was supported in part by US Public Health Service Research Grant HL-93399 from the Heart and Lung Institute and by National Institute Contract Nol-CP-55606 to J.P. This is communication No. 378 from the Joan and Lester Avnet Institute of Molecular Biology.Predoctoral fellow in the Medical Scientist Training Program (United States Public Health Service Grant 5-TO-5-GM 01669-12) at the New York University School of Medicine.Recipient of a grant-in-aid from the New York Heart Association.     

Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.     

Identity of the 19S 'prosome' particle with the large multifunctional protease complex of mammalian cells (the proteasome)

There have been many reports that eukaryotic cells contain ring-shaped 19S or 20S particles which are composed of numerous polypeptide subunits ranging in size between 25 and 35 kilodaltons. Because these particles seemed to copurify with inactive mRNA, they were assumed to function in regulating mRNA translation and hence were named 'prosomes' (for 'programmed-o-some'). A number of properties have been reported for these structures, including an association with specific RNA species or with certain heat-shock proteins and involvement in tRNA processing or aminoacyl tRNA synthesis. However, these proposed activities have not been supported by definitive evidence. During studies of the proteolytic systems in mammalian tissues, we noted many similarities between these 19S particles and the high molecular weight protease complexes that are present in most or all eukaryotic cells. This (700 kilodalton) enzyme complex, designated here as LAMP for 'large alkaline multi-functional protease', contains three distinct endoproteolytic sites which function at neutral or alkaline pH and are specific for hydrolysis of proteins, hydrophobic peptides, or basic peptides. This protease also exists in a latent form which can be activated by polylysine, fatty acids, or ATP. In this report, we show that the prosomes and these protease complexes are very similar or identical with respect to their size, polypeptide composition, immunological cross-reactivity, appearance in the electron microscope, radial symmetry of subunits, subcellular localization, and proteolytic activities. Therefore, the 'prosome' probably plays a critical role in intracellular protein breakdown, and we propose that it be renamed 'proteasome'.     

An excitatory component of the jaw opening reflex in the temporal and masseter muscles of cats and monkeys

Résumé Après stimulation électrique de la gencive chez le singe et du nerf lingual chez le chat, une réponse réflexe de courte latence à été enregistrée au niveau du muscle temporal et du masseter. La latence de cette réponse est plus rapide que celle de la réponse digastrique induite par le même stimulus. La réponse temporale de courte latence peut également être observée en l'absence tant d'une réponse digastrique que du réflexe d'ouverture de la gueule.

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This investigation was supported by U.S. Public Health Service Grant No. NS 08604.L. J. Goldberg holds U.S. Public Health Service Career Development Award No. 5 K04 DE11616. The technical assistance of MissSheryl K. Simms is greatly appreciated.     

Does tenotomy of skeletal muscle alter Z-line width in older animals?

Summary Results of unilateral achilles tenotomy on older (350–410 g) male rats, showed that the general width of Z-lines in the tenotomized muscles was not significantly altered by this procedure. Streaming of the Z-lines and rod formations was still present, as in younger rats.This investigation was supported in part by NIH grants 1-RO1-NS-14033 and 1-T32-07224.     

Evidence for dynamically organized modularity in the yeast protein-protein interaction network

In apparently scale-free protein-protein interaction networks, or 'interactome' networks, most proteins interact with few partners, whereas a small but significant proportion of proteins, the 'hubs', interact with many partners. Both biological and non-biological scale-free networks are particularly resistant to random node removal but are extremely sensitive to the targeted removal of hubs. A link between the potential scale-free topology of interactome networks and genetic robustness seems to exist, because knockouts of yeast genes encoding hubs are approximately threefold more likely to confer lethality than those of non-hubs. Here we investigate how hubs might contribute to robustness and other cellular properties for protein-protein interactions dynamically regulated both in time and in space. We uncovered two types of hub: 'party' hubs, which interact with most of their partners simultaneously, and 'date' hubs, which bind their different partners at different times or locations. Both in silico studies of network connectivity and genetic interactions described in vivo support a model of organized modularity in which date hubs organize the proteome, connecting biological processes--or modules--to each other, whereas party hubs function inside modules.     

Rocket UV flash spectra from the solar eclipse of March 7, 1970

Flash spectra of the total solar eclipse throughout all its phases have been obtained in the extreme ultraviolet for the first time.     

Structure of the Sec23/24-Sar1 pre-budding complex of the COPII vesicle coat

COPII-coated vesicles form on the endoplasmic reticulum by the stepwise recruitment of three cytosolic components: Sar1-GTP to initiate coat formation, Sec23/24 heterodimer to select SNARE and cargo molecules, and Sec13/31 to induce coat polymerization and membrane deformation. Crystallographic analysis of the Saccharomyces cerevisiae Sec23/24-Sar1 complex reveals a bow-tie-shaped structure, 15 nm long, with a membrane-proximal surface that is concave and positively charged to conform to the size and acidic-phospholipid composition of the COPII vesicle. Sec23 and Sar1 form a continuous surface stabilized by a non-hydrolysable GTP analogue, and Sar1 has rearranged from the GDP conformation to expose amino-terminal residues that will probably embed in the bilayer. The GTPase-activating protein (GAP) activity of Sec23 involves an arginine side chain inserted into the Sar1 active site. These observations establish the structural basis for GTP-dependent recruitment of a vesicular coat complex, and for uncoating through coat-controlled GTP hydrolysis.