Signatures of β-sheet secondary structures in linear and two-dimensional infrared spectroscopy

Using idealized models for parallel and antiparallel β sheets, we calculate the linear and two-dimensional infrared spectra of the amide I vibration as a function of size and secondary structure. The model assumes transition–dipole coupling between the amide I oscillators in the sheet and accounts for the anharmonic nature of these oscillators. Using analytical and numerical methods, we show that the nature of the one-quantum vibrational eigenstates, which govern the linear spectrum, is, to a large extent, determined by the symmetry of the system and the relative magnitude of interstrand interactions. We also find that the eigenstates, in particular their trends with system size, depend sensitively on the secondary structure of the sheet. While in practice these differences may be difficult to distinguish in congested linear spectra, we demonstrate that they give rise to promising markers for secondary structure in the two-dimensional spectra. In particular, distinct differences occur between the spectra of parallel and antiparallel bsheets and between β hairpins and extended β sheets.

Elsinore fault seismicity: The September 13, 1973, Agua Caliente Springs, California, earthquake series

A relatively small M_L = 4.8 earthquake and its aftershock series on the southern portion of the Elsinore Fault Zone in eastern San Diego County, California, provided a rare opportunity to study an area that has been subjected to variable tectonic interpretations in the past. Within 12 to 26 hours after the main shock, a network of four portable seismograph stations was established around the main event near Agua Caliente Springs to supplement the stations of the Southern California Seismographic Network. Four days after the main shock, seven additional portable seismograph stations were installed. In addition to the main event, 45 subsequent events were studied, ranging in magnitude from about 1.0 to 3.7. Of these, 36 could be termed aftershocks by their close proximity to the main event, whose proper location was determined by analysis of the aftershock series. Of the two branches of the Elsinore Fault in this region, the south branch is associated with the earthquake series. Focal mechanisms are consistent with right-lateral strike-slip along the south branch, with northeast dip at latitude 32°51′N. These conclusions are supported by hypocentral locations. Thrust activity on the two fault branches may be developing a horst between them, accounting for elevation and tilt changes observed near Agua Caliente

Golden Shiner, Bluegill, and Green Sunfish Production in a small Lake

A small lake located 43 miles southeast of Dallas in Kauf­man County, owned by Dr. Ozro T. Woods, was treated with rotenone in February, 1952. With a surface area of about two acres, the lake contained 5.4 acre-feet of water, with a maximum depth of six feet. It was constructed in 1947 and filled the same year

Vibrational Spectra of a Mechanosensitive Channel

We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the transmembrane helices, which is changing during the opening process. Linear dichroism cannot distinguish an intermediate structure from the closed structure, but sum-frequency generation can. In addition, we find that two-dimensional infrared spectroscopy can be used to distinguish all three investigated gating states of the mechanosensitive membrane channel.

A Pleistocene Molluscan Fauna Near Byers, Clay County, Texas

Fossil fresh-water and land mollusks are described from a Pleistocene alluvial deposit near Byers, in Clay County, Texas-an ancient lake-bed formed by an ox-bow cut-off during the meandering of the Red River. Using as indicators recognized faunas which are identified with known geological ages in the mid-continent region of the United States, a comparative study chart and vertical-range graph were made of the Byers shells to determine age of deposition. This comparative-study method dated the shell deposit back to an Illinoian age. The molluscan fauna indicates during this time a more humid and cooler climate without the summer high temperatures which prevail in the same area today

An Ecological Comparison of the Ben Franklin and Clear Creek Local Molluscan Faunas in Texas

Radiocarbon tests date the Ben Franklin local fauna as Wisconsin, and the Clear Creek local fauna as Sangamon. The contrast between the mollusks of these two faunas is remarkable, as shown by the following table

Color Phases In Helicina Orbiculata Tropica \u27Jan\u27 Pfr.

An interesting shell-color phase occurs in Helicina orbiculata tropica ’Jan.’ Pfr., a small land snail found in abund ance in northeastern, southern, and central Texas. Pilsbry and Ferris have noted color variations in this species, stating that some colonies are all white; others are mingled with red or blue shells

Notes on the Alluvial History of the Lampasas River, Texas

Excavations made in connection with the Stillhouse Hollow Dam construction in Bell County, Texas, offered an excellent view of almost complete sections of the floodplain and the two terraces developed in the valley at this point. In the process of work sponsored by the National Park Service, these sections were measured and their lithology recorded. A molluscan fauna was recovered from approximately two tons of sediments quarried from a shallow zone near the base of the T-1 terrace. A radio-carbon date from shells higher in the same terrace indicates an age of 4970 ± 250 B.P., according to the determination of Dr. Meyer Rubin of the U.S. Geological Survey. The tests were run on valves of Tritogonia verrucosa (Barnes), Quadrula pustulosa Lea, and Amblema perplicata (Conrad)