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

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

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)

Ecological Observations Upon the Fresh-Water Sponges in Dallas County, Texas

Published distributional and ecological data on the fresh-water sponges of Texas are meager. Besides Marcus Old\u27s (1936) report on sponges collected by us the only other published report for this region is a description of Asteromyenia plumosa by Weltner (1895) from McKinney, Collin County, Texas. Dr. Old reported Spongilla fragilis from a small pond 1½ miles west of Dallas, and from Parson\u27s Slough near Seagoville in Dallas County; Trochospongilla horrida from Elm Fork of the Trinity River, Dallas County; Asteromyenia plumosa from White Rock Lake, Dallas; and Ephydatia crateriformis from the East Fork of the Trinity River in Rockwall County. The Southwest presents an environmental situation quite different from that in the northern and eastern sections of the United States. These sectional differences are shown in the physical appearance, growth and gemmule production of fresh-water sponges. We report here data collected by us from 1932 to 1952. A taxonomic key to the six species found near Dallas is also presented. We are indebted to Professor Marcus Old of Ursinus College for verifying or correcting our identifications

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

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.

Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.