Site-saturation studies of β-lactamase: Production and characterization of mutant β-lactamases with all possible amino acid substitutions at residue 71

A mutagenic technique that "saturates" a particular site in a protein with all possible amino acid substitutions was used to study the role of residue 71 in β-lactamase (EC 3.5.2.6). Threonine is conserved at residue 71 in all class A β-lactamases and is adjacent to the active site Ser-70. All 19 mutants of the enzyme were characterized by the penam and cephem antibiotic resistance they provided to Escherichia coli LS1 cells. Surprisingly, cells producing any of 14 of the mutant β-lactamases displayed appreciable resistance to ampicillin; only cells with mutants having Tyr, Trp, Asp, Lys, or Arg at residue 71 had no observable resistance to ampicillin. However, the mutants are less stable to cellular proteases than wild-type enzyme is. These results suggest that Thr-71 is not essential for binding or catalysis but is important for stability of the β-lactamase protein. An apparent change in specificity indicates that residue 71 influences the region of the protein that accommodates the side chain attached to the β-lactam ring of the substrate

The effect of cave illumination on bats

Artificial light at night has large impacts on nocturnal wildlife such as bats, yet its effect varies with wavelength of light, context, and across species involved. Here, we studied in two experiments how wild bats of cave-roosting species (Rhinolophus mehelyi, R. euryale, Myotis capaccinii and Miniopterus schreibersii) respond to LED lights of different colours. In dual choice experiments, we measured the acoustic activity of bats in response to neutral-white, red or amber LED at a cave entrance and in a flight room – mimicking a cave interior. In the flight room, M. capaccinii and M. schreibersii preferred red to white light, but showed no preference for red over amber, or amber over white light. In the cave entrance experiment, all light colours reduced the activity of all emerging species, yet red LED had the least negative effect. Rhinolophus species reacted most strongly, matching their refusal to fly at all under any light treatment in the flight room. We conclude that the placement and light colour of LED light should be considered carefully in lighting concepts for caves both in the interior and at the entrance. In a cave interior, red LED light could be chosen – if needed at all – for careful temporary illumination of areas, yet areas important for bats should be avoided based on the precautionary principle. At cave entrances, the high sensitivity of most bat species, particularly of Rhinolophus spp., towards light sources almost irrespective of colour, calls for utmost caution when illuminating cave entrances

Discovery of meteorites on a blue-ice field near the Frontier Mountains, North Victoria Land, Antarctica

A high concentration of meteorites were discovered on a blue ice field northeast of the Frontier Mountains. As a result of a systematic search, a total of 42 meteorites were recovered. The current glacial situation has evolved through various stages, which are discussed in relationship to the concentration of meteorites. Ice flow patterns are summarized. The chemical composition and terrestrial ages of the meteorites are discussed

Studies in matter antimatter separation and in the origin of lunar magnetism

A progress report, covering lunar and planetary research is introduced. Data cover lunar ionospheric models, lunar and planetary geology, and lunar magnetism. Wind tunnel simulations of Mars aeolian problems and a comparative study of basaltic analogs of Lunar and Martial volcanic features was discussed

Eastern Airlines: The Rise and Fall of The Wings of Man

This paper examines the rise and fall of Eastern Airlines from 1928 to 1991. lt outlines the carrier\u27s development under a succession of leaders and discusses the major events of each leader\u27s reign. From a small contract mail carrier known as Pitcairn Aviation, Eastern grew to become one of the largest airlines in the free world. But after 26 years of growth and prosperity under the leadership of Eddie Rickenbacker, the airline began to stumble in the early 1960s. Frank Lorenzo took the reins in 1986 and began selling the carrier\u27s assets while attempting to destroy the unions. After a massive employee strike in 1989 and a bout with bankruptcy, Eastern stopped flying in January 1991

Topics concerning state variable feedback in automatic control systems. Part 1 - Specification. Part 2 - Sensitivity. Part 3 - Intentional nonlinearities. Part 4 - Unavailable states

Specifications, sensitivity, intentional nonlinearities, and unavailable states concerned with state variable feedback in automatic control system

A 'p-n' diode with hole and electron-doped lanthanum manganite

The hole-doped manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 undergo an insulator to metal transition at around 250 K, above which both behave as a polaronic semiconductor. We have successfully fabricated an epitaxial trilayer (La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3), where SrTiO3 is an insulator. At room temperature, i.e. in the semiconducting regime, it exhibits asymmetric current-voltage (I-V) characteristics akin to a p-n diode. The observed asymmetry in the I-V characteristics disappears at low temperatures where both the manganite layers are metallic. To the best of our knowledge, this is the first report of such a p-n diode, using the polaronic semiconducting regime of doped manganites.Comment: PostScript text and 2 figures, to be published in Appl. Phys. Lett

A NEW GIANT CAMEL, TITANOTYLOPUS NEBRASKENSIS, gen. et sp. nov.

The purpose of this bulletin is to figure and describe a .amel brought to light in the field season of 1933, which seems to be the giant of all camels found in the State. The specimen consists of the right ramus with the symphysial portion. The mandible is 26% inches long, or about the length of one\u27s outstretched arm to the finger tips. This jaw is nine inches longer than that of Camelops kansanus. Such an extraordinary jaw indicates a camel nearly twice as large as Alticamelus altus. In reference to its unusual size we are proposing for it the name Titanotylopus nebraskensis. The teeth are very brachyodont, and the incisors are not spatulate. The dental formula of T-itanotylopus nebraskensis reads as follows: i 3, c 1, p 2, m 3. The third incisor was practically aborted as indicated by the small and very shallow alveolus crowded close to the base of the canine. The first left incisor has the enamel preserved on the inner side. It measures but 19 mm. in height. It should be noted that in Pliauchenia the cheek teeth are subbrachyodont to hypsodont; in M egatylopus they are more or less hypsodont; and in Titanotylopus they are distinctly brachyodont. Obviously premolars 1 and 2 have long been missing in this genus for not a vestige of them has been left. Such an assemblage of characters seems well beyond the realm of mere variation, and we find no ready escape from making this a new genus. So few genera of camels are reported as yet from the Pleistocene that Titanotylopus deserves the more attention. This unusual specimen was secured during the first week in September, 1933, by Frank Crabill (Class of 1935), a member of the Morrill Palaeontological Expedition of 1933, but was found, collected, and donated by Mr. and Mrs. S. E. Jensen of Red Cloud who found it in a small pit about eight miles northwest of Red Cloud, Webster County, Nebraska. The exact location of this pit is the N.W.1,4, Sec. 17, T. 2 N., R. 11 W. The jaw was found 33 feet below the surface in Pleistocene gravel of supposed Kansan age, and is accessioned 1-6-9-33, the Nebraska State Museum. The specimen consists of the right ramus of the mandible together with the symphysis intact, the dentition being complete but damaged by exposure