Walter J. Moore

Isolation and partial characterization of rat brain synaptic plasma membranes

Abstract— Synaptic plasma membranes from the cortices of adult rat brain were isolated from synaptosomes prepared by flotation of a washed mitochondrial pellet (P2) in a discontinuous Ficoll‐sucrose gradient. Contamination of the synaptosome fraction by microsomes was estimated by enzymic and chemical analysis to be less than 15 per cent. (2) The purified synaptosome fraction was subjected to osmotic shock, subfractionated on a discontinuous sucrose gradient and the distribution of enzymic and chemical markers for synaptic plasma membranes, microsomal membranes and mitochondria was determined. (3) Comparison of synaptosome subfractions prepared in the presence and absence of 1 mM NaH2 PO4/0.1 mM EDTA buffer pH 7.5, indicated that the ionic composition of the isolation medium markedly affected the distribution and enzymic composition of the subfractions. (4) Synaptic plasma membranes prepared in the presence of PO4/EDTA exhibited a 10‐fold enrichment in [Na++ K+] ATPase and were characterized by less than 15 and 10 per cent contamination by microsomes and mitochondria respectively. (5) The polypeptide composition of the purified synaptic plasma membranes was compared with the microsomes and mitochondria by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. No differences between the protein and glycoprotein composition of the synaptic plasma membranes and microsomes were detected. The mitochondria, in contrast, possessed a unique protein composition.

Thermodynamics of the Formation and Migration of Defects in Cuprous Oxide

The number of gram atoms of excess oxygen y per mole of cuprous oxide has been measured by means of a quartz‐fiber microbalance. The combined pressure and temperature dependence is log10 y=0.27 log10PO2—(21.7 kcal) / RT+0.29 with T in °K and PO2 in mm Hg. This relation has been utilized to determine the extent of the cuprite field in the copper‐oxygen system. The cation vacancy V+ is formed in Cu2O by the reaction ¼O2→½O=+VCu+. The entropy of formation of the vacancy, computed from ΔS=12S(O=)+S(V+)−14S(O2) is S(V+) = 12.1 cal deg—1. This positive entropy, caused by the lowering of the vibration frequencies of neighboring copper atoms, is the principal factor responsible for the defect structure of cuprous oxide. The new thermodynamic data lead to a quantitative determination of the diffusion parameters for copper in Cu2O.

Electrical Conductivity of Monocrystalline Cuprous Oxide

The electrical conductivity σ of single crystals of cuprous oxide was measured from 25° to 1100°C and at oxygen pressures PO2 from 10—5 to 760 mm. Except at very low PO2 the σ at all T is due entirely to positive holes associated with native defects (cation vacancies). The different activation energies which occur in different temperature regions can be quantitatively interpreted on this basis. For example, in 1.4 mm O2 and T above 750°C, σ=2.3×103 exp(−e1/kT) with e1=0.625 ev. This e1=e3+(ΔH/2), where ΔH is the heat of solution of an atom of oxygen and e3 is the activation energy for motion of positive holes in an electric field (e3=0.295 ev and ΔH=0.63 ev). Polycrystalline cuprous oxide doped with beryllium displayed a conductivity consistent with an increase in vacancies and decrease in free positive holes due to incorporation of Be2+.

Diffusion of Nickel in Nickel Oxide

Diffusion coefficients for nickel in polycrystalline and monocrystalline nickel oxides have been measured by the surface‐activity method from 1000 to 1400°C in air. Within experimental uncertainty the values D=4.4×10—4 exp(—44.2/RT) fit both cases. These results indicate that the oxidation of nickel under comparable conditions of T and P proceeds via lattice diffusion of Ni through NiO.

Binding of [125I]-α bungarotoxin to particulate fractions of rat and guinea pig brain

Summary Binding of α-bungarotoxin to rat and guinea pig brain particulates is used to assay the nicotinic acetylcholine receptor as 3.4 and 2.1 pmol/g brain respectively. Postnatal development shows a continual increase of receptor (to 40 days) with a peak specific activity around 10 days.

PROPERTIES OF ACETYLCHOLINESTERASE FROM RAT BRAIN

—Acetylcholinesterase (EC 3.1.1.7) from cerebral cortex of mature rats was purified by means of affinity chromatography, to a specific activity of 4.5 mmol acetylthiocholine hydrolysed × min−1× mg−1 protein. The enzyme is a glycoprotein and contains a single subunit with a mol. wt of about 80,000. Electrofocusing either a pure or a crude preparation of the enzyme produces six enzymatically active bands with a range of isoelectric points from 5.04 to 5.54. Gel filtration yields oligomers with molecular weights of about 150,000, 320,000, 500,000 and 650,000, with 60 per cent of the activity in the 150,000 fraction. The gel fractions with molecular weights 150,000 and 320,000 produce the same isoelectric patterns. Different subcellular fractions of the cortex show different characteristic isoenzyme patterns.

Sputtering of Silver by Light Ions with Energies from 2 to 12 kev

Electromagnetically analyzed ionic beams from a radio‐frequency source were used to study the sputtering yield S (atoms per ion) for light ions normally incident on silver targets at energies from 2 to 12 kev. The yields displayed broad maxima with energy in the range studied. At 5 kev the following values of S were found: H+, 0.035; D+, 0.090; H2+, 0.077; D2+, 0.21; H3+, 0.11; D3+, 0.33; He+, 0.48; N+, 4.0; O+, 4.4; Ne+, 5.5. The angular distribution of sputtered silver followed a cosine dependence about the normal to the target surface even when the beam hit the target at oblique incidence.

Paramagnetic Resonance and Optical Properties of Amethyst

Color centers in amethyst are produced by action of ionizing radiation on precursor centers which arise from substitution of Fe3+ for Si4+ in the α‐quartz structure, with charge neutralization usually achieved by an alkali‐metal ion on the twofold axis of the center. These Fe3+ centers provide the dominant features of the electron paramagnetic resonance spectrum of amethyst, which was measured in the X‐band at room and liquid‐nitrogen temperatures. The spectrum was fitted to an orthorhombic spin Hamiltonian with g=2.0032, D=−2.0463, E=5.5277, F=−0.0282 Gc/sec. The optical biaxiality of amethyst, with biaxial angle 2V=6 to 12°, is due to unequal occupation of the three equivalent Si4+ sites in the structure by Fe3+ during crystal growth. This phenomenon may help to specify geological conditions during hydrothermal growth of natural amethyst.

Diffusion and Exchange of Zinc in Crystalline Zinc Oxide

The exchange of zinc vapor with crystals of zinc oxide has been measured between 900 and 1025°. The ZnO crystals, incorporating radioactive Zn65, were prepared by the reaction of zinc vapor and atmospheric oxygen. A sample of the crystals was weighed into a small quartz bucket suspended in a cylindrical quartz vessel. After addition of enough pure zinc to give the requisite vapor pressure, the vessel was evacuated and sealed. The ZnO sample contained about 1000 acicular crystals, with a mean diameter of 0.01 mm and a selected narrow distribution of diameters. At different times the bucket was withdrawn, and the residual radioactivity of the ZnO was determined. Except for the initial stages, the exchange reaction appeared to be controlled by the diffusion of Zn in ZnO. The diffusion coefficient D was calculated at 1 atmos zinc pressure as D = 4.8 exp(—73.0 kcal/RT) cm2 sec—1. Variation of zinc pressure from 0.2 to 2.0 atmos showed that D varies as PZn0.65, suggesting that the diffusing species is the singl...

Irreversible binding of a krait neurotoxin to membrane proteins from eel electroplax and hog brain.

Abstract A neurotoxin of molecular mass M ∼ 7600 dalton was separated from venom of Bungarus fasciatus and iodinated with 125I of high specific activity. The radioactive bungarotoxin bound irreversibly to protein fractions extracted from eel electroplax and hog cerebral cortex by sodium deoxycholate solutions of low ionic strength. In both cases the toxin was bound to single protein fractions that eluted from Sephadex G-100 columns in the range M = 50000 to 80000. The results indicate that brain contains an acetylcholine receptor similar to that in tissues derived from muscle.