Apparent Linewidth Research Articles

The behavior of holo- and apo-forms of bovine superoxide dismutase at low pH

1. 1. Holo-superoxide dismutase from bovine erythrocytes has been shown to undergo a reversible structural modification in the pH 3–5 range. 2. 2. The spectral alterations observed on changing from neutrality to pH 3 were: a slight attenuation of the 680 nm absorbance; the loss of the 450 nm shoulder, apparent in the optical spectrum of the native protein; and a new band appeared at 330 nm. The circular dichroism at 600 nm was essentially lost while a weak negative band appeared at approx. 380 nm and a positive band at 310 nm. 3. 3. The EPR spectrum was also modified on changing from the native to the low pH form: A | increased from ≈ 130 to ≈ 150 G, g | remained unchanged at ≈ 2.27, and g m decreased from ≈ 2.09 to ≈ 2.08. The apparent linewidth remained essentially constant. 4. 4. High resolution (220 MHz) PMR spectra of holo- and apoproteins revealed that the metals influence the three-dimensional structure of the protein. 5. 5. PMR studies indicated that at pH 3 the apoprotein existed almost entirely in a random coil form and that it assumed a compact well-ordered structure on returning to neutral pH. The holoprotein maintained a compact, apparently dimeric, structure even at pH 3.

Konformative beweglichkeit flexibler ringsysteme. Untersuchungen mit hilfe der protonenresonanz-spektroskopie—VI. Mitteilung: Eine erweiterung und verfeinerung des verfahrens zur bestimmung der aktivierungsenergie

The methods to evaluate the lifetime of conformative molecular states by measurementsof the temperature dependence of proton resonance, have been refined and extended. For this purpose, the apparent line width is divided into two components, the temperature dependence of each being studied. It is shown, that also that part of the total line width which is not influenced by the exchange, the “Eigenbreite”, depends on temperature. The temperature dependence of the “Eigenbreite” has to be considered when using the various methods for the determination of τ, especially when the “Eigenbreite” is relatively large compared to the chemical shift. The efficiency of the method is demonstrated for some examples, i.e. ring compounds, for which the proton resonance signals of two pairs of geminal ligands, on different places in the ring system, can be analysed separately.

Two Uses of Probability Paper in Scintillation Gamma-Ray Spectroscopy

Probability paper can greatly facilitate scintillation gamma spectroscopy because plots of reliable peaks on such paper, as percentage of toal counts vs. pulse height, show straight lines can be used (1) to measure the internal consistency of the performance of the spectrometer electronic gear and (2) to determine the photopeak width at half-maximum. The relative slope of the straight line is a measure of the apparent line width or percentage energy resolution of the spectrometer. An example of this method is given in which the Cs137 gamma spectrum as recorded by an NaI crystal is analyzed.

Double Modulation System for Narrowing Electron Resonance Absorption Lines

A method is presented for observing electron resonance absorption on an oscilloscope screen by using both a magnetic field modulation and a klystron frequency modulation. This is distinguished from the usual system of keeping the klystron frequency fixed and modulating the magnetic field by the fact that the apparent line width observed on the oscilloscope is narrower than that observable by a single (magnetic or frequency) modulation. An equation is derived relating the apparent line width (double modulation) to the true line width (single modulation). Reductions by a factor of 17 can be easily obtained. As a result paramagnetic absorption lines ordinarily too wide to be observed within the width of the resonant cavity containing the sample can be observed within the cavity resonance. It is believed that this double modulation system might be advantageous in oscilloscope searching for new paramagnetic absorptions.

Cathode-Ray Tube Terminology

This paper offers tentative definitions for many terms commonly used in cathode-ray tube work. The terms defined are magnetic deflection sensitivity, electrostatic deflection sensitivity, gun-current efficiency, electron gun, screen, screen luminous efficiency, screen actinic efficiency, screen radiant efficiency, spectral characteristic, relative radiant energy, color characteristic, visual spectral characteristic, actinic spectral characteristic, persistence characteristic, relative brilliance, candle power distribution characteristic, luminescence, phosphorescence, fluorescence phosphor, defocus, spot distortion, pattern distortion, spot size, spot diameter, line width, apparent spot size, apparent spot diameter, and apparent line width. The methods of measurement of gun-current efficiency, screen luminous efficiency, candle power, screen, actinic efficiency, screen radiant efficiency, spectral characteristic, persistence characteristic, candle power distribution characteristic, spot size, spot distortion, and pattern distortion are also included for clarifying purposes.