The effect of protein backbone hydration on the amide vibrations in Raman and Raman optical activity spectra

Raman and specifically Raman optical activity (ROA) spectroscopy are very sensitive to the solution structure and conformation of biomolecules. Because of this strong conformational sensitivity, density functional theory (DFT) calculations are often used to get a better understanding of the experimentally observed spectral patterns. While e.g. for carbohydrate structure the water molecules that surround the solute have been demonstrated to be of vital importance to get accurate modelled ROA spectra, the effect of explicit water molecules on the calculated ROA patterns of peptides and proteins is less well studied. Here, the effect of protein backbone hydration was studied using DFT calculations of HCO-(l-Ala)(5)-NH2 in specific secondary structure conformations with different treatments of the solvation. The effect of the explicit water molecules on the calculated spectra mainly arises from the formation of hydrogen bonds with the amide C?O and N-H groups. Hydrogen bonding of water with the C?O group determines the shape and position of the amide I band. The C?O bond length increases upon formation of C?OH2O hydrogen bonds. The effect of the explicit water molecules on the amide III vibrations arises from hydrogen bonding of the solvent with both the C?O and N-H group, but their contributions to this spectral region differ: geometrically, the formation of a C?OH2O bond decreases the C-N bond length, while upon forming a N-HH2O hydrogen bond, the N-H bond length increases

Responses to hypovolaemic thirst in gerbils

In the present study, a series of experiments were conducted to examine how the gerbil responds to an extracellular challenge. Adult female gerbils, weighing from 50 gm. to 70 gm., were either exposed to a 10% (vol x wt) polyethelene glycol injection, or a vehicle control injection. Within each injection level, half of the animals had access· to water after injection, while the other half had access to a .9% saline solution. There was a significant increase in fluid intake associated with injection dosages and animals drank significantly more when exposed to saline than when exposed to water. It was concluded that the gerbil responds to an extracellular insult in a similar manner as the rat. Hematocrit values, taken at 12 and 24 hours after injections, provide a supportive. interpretive corollary to the fluid intake data. Delayed access to fluids following injections resulted in an inconsistent fluid intake trend.It was postulated that an additional regulatory mechanism of a limited efficiency range was operating in conjunction with fluid intake to produce this inconsistency

A Child of the Atlantic: The Maine Years of John Brown Russwurm

Celebrated in life as co-founder of America’s first black newspaper, John Brown Russwurm was the embodiment of an Atlantic Creole. Born in Jamaica to a white American father and a black Jamaican mother, as a young man Russwurm moved to North America. Throughout his teens and twenties, his “home” was southern Maine, and he was given a good secondary education there. After finishing school, Russwurm taught in several black schools in Philadelphia, New York City, and Boston. It was in these cities that he came into contact with America’s free black leaders, some of whom supported the movement to colonize black Americans in West Africa or Haiti. After teaching for several years, he returned to Maine to attend college, and, in 1826, he became the first African American to graduate from Bowdoin College. By the time he graduated from college he had become a staunch supporter of the colonizationist movement. Initially he hoped to settle in Haiti, but, when that fell through, he moved across the Atlantic to the West African nation of Liberia, a settler colony for American blacks. In light of Russwurm’s transnational background, his ultimate relocation to Africa was a logical extension of his life’s trajectory. The author is an associate professor in the School of Humanities at Pennsylvania State University-Harrisburg. This article is part of his research on trans-Atlantic communication networks among nineteenth-century blacks. His most recent publication is “Tradition of Dissent: West Indians and Liberian Journalism, 1830-1970,” Ecquid Novi: African Journalism Studies, vol. 33, no. 2 (2012). He may be reached at [email protected]

Alternative piezoresistor designs for maximizing cantilever sensitivity.

Over the last 15 years, researchers have explored the use of piezoresistive microcantilevers/resonators as gas sensors because of their relative ease in fabrication, low production cost, and their ability to detect changes in mass or surface stress with fairly good sensitivity. However, existing microcantilever designs rely on irreversible chemical reactions for detection and researchers have been unable to optimize symmetric geometries for increased sensitivity. Previous work by our group showed the capability of T-shaped piezoresistive cantilevers to detect gas composition using a nonreaction-based method – viscous damping. However, this geometry yielded only small changes in resistance. Recently, computational studies performed by our group indicated that optimizing the geometry of the base piezoresistor increases device sensitivity up to 700 times. Thus, the focus of this work is to improve the sensitivity of nonreaction-based piezoresistive microcantilevers by incorporating asymmetric piezoresistive sensing elements in a new array design. A three-mask fabrication process was performed using a 4 silicon-on-insulator wafer. Gold bond pads and leads were patterned using two optical lithography masks, gold sputtering, and acetone lift-off techniques. The cantilevers were patterned with electron-beam lithography and a dry etch masking layer was then deposited via electronbeam evaporation of iron. Subsequently, the silicon device layer was deep reactive ion etched (DRIE) to create the vertical sidewalls and the sacrificial silicon dioxide layer was removed with a buffered oxide etch, completely releasing the cantilever structures. Finally, the device was cleaned and dried with critical point drying to prevent stiction of the devices to the substrate. For the resonance experiments, the cantilevers were driven electrostatically by applying an AC bias, 10 Vpp, to the gate electrode. A DC bias of 10 V was placed across the piezoresistor in series with a 14 kÙ resistor. The drive frequency (0 – 80 kHz) was swept until the cantilever resonated at its natural frequency, which occurred when the output of the lock-in amplifier reached its maximum. These devices have been actuated to resonance under vacuum and their resonant frequencies and Qfactors measured. The first mode of resonance for the asymmetric cantilevers was found to range between 40 kHz and 63 kHz, depending on the piezoresistor geometry and length of the cantilever beam. The redesigned piezoresistive microcantilevers tested yielded static and dynamic sensitivities ranging from 1-6 Ù/Ìm and 2-17 Ù/Ìm displacement, respectively, which are 40 –730 times more sensitive than the best symmetric design previously reported by our group. Furthermore, the Q-factors ranged between 1700 and 4200, typical values for MEMS microcantilevers

Physical and chemical attributes of a genetically modified fruit pectin

Pectin is an important polymer used in the food industry as a thickening and gelling agent. Though pectin is ubiquitous in plants, chemical and structural differences among pectin molecules prevent most from being viable for industrial use. Enzymes found naturally in fruit cell walls during the ripening process impair many desirable attributes of fruit pectins, rendering them unsuitable for industrial applications. Pectin methylesterase (PME) is one such enzyme whose expression can be altered during ripening through the use of recombinant genetic engineering. Reduction in levels of PME results in increased degree of methylation and molecular size of pectin, greatly increasing the favorable quality attributes of processed tomato products, primarily viscosity. Reduction in PME activity also alleviates calcium deficiency-related disorders such as blossom end rot, generating savings from greater harvest yields. We hypothesize that an optimum level of PME activity exists such that the processing attributes and quality characteristics of tomato fruit pectins are optimized for industrially viable use. Steady-state shear ramps were performed to discern differences in rheology between prepared tomato samples of varying PME activity and ripeness stage, for whole tomato juice, separated juice serum, and tomato juice solids reconstituted with both water and tomato serum. Our results show that a reduction in PME activity greatly increases the final viscosity of prepared tomato samples, and the maturation process decreases overall viscosity through the degradation and demethylation pf plant cell walls and pectins. The difference in viscosity for juice was more distinct than that for serum, indicating the importance of PME activity on the fruit cell wall and water-insoluble pectins. Nuclear Magnetic Resonance (NMR) spectra and Gas Chromatography (GC) both indicated the presence of galacturonic acid residues in tomato serum, and NMR showed that these galacturonic acid residues are indeed from pectin. Furthermore, NMR spectra confirmed the effectiveness in down-regulating PME and its impact on the degree of methylation of serum pectins, confirming with rheological measurements that increased DM of pectin yields higher viscosity products. Practical application of this information will prove valuable in understanding the effect of genetically regulating enzyme activity in vivo and determining the optimal level of PME for creating tomato products with desirable quality attributes. Furthermore, the present work seeks to use tomato pectin as a model system for elucidating information regarding the relationship between genetic alterations of pectin and the effect on its chemical structure which affects the physical and functional attributes

Academic Success and Curricular Structure: Exploring the Relationship Between Prerequisite Course Sequence and Grade Point Average in Community College Health Science Students

The current and ongoing shortage of healthcare professionals in the United States challenges educators and institutions to produce graduates of health professions programs in ever-increasing numbers. However, the current process typically used in community colleges is a cafeteria-style system of open enrollment, a model in which students pick courses from many choices without guidance or counseling. As a result, students often enroll in more advanced courses before taking the fundamental science courses. This may lead to poor performance, dropout, or failure. One potentially important variable in student success at a community college in the southwestern United States is student performance in the prerequisite course sequence in the health science curriculum. In this study, a prerequisite course is a course in the health sciences curriculum required for application to one of the health professions programs at South Community College; prerequisite grade point average (PGPA) is a student’s grade point average in the health professions related science (HPRS) courses. PGPA is a commonly used criterion for admission to health professions programs. This study was therefore designed as a quantitative retrospective analysis of health professions related science prerequisite course sequence and PGPA. This study was designed to produce empirical data to support proposed curricular innovations and strategies at the study site. The study findings demonstrated statistically significant relationships between course sequence and PGPA. These data may be applied to formulate strategies directed at resolving issues that negatively affect enrollment, academic success, and graduation rates of students in the health sciences at South Community College. Keywords: Prerequisite Grade Point Average (PGPA), Health Professions Related Science (HPRS), course sequenc

Feeding practices and growth among young children during two seasons in rural Ethiopia

BACKGROUND: The use of indices of infant and young child feeding practices to predict growth has generated inconsistent results, possibly through age and seasonal confounding. The aim of this study was to evaluate the association of a dietary diversity score (DDS) and infant and child feeding index (ICFI) with growth among young children in a repeated cross-sectional and a follow-up study in two distinct seasons in rural southwest Ethiopia. METHODS: We used a repeated cross-sectional design comparing child feeding practices to nutritional status in 6–12 month old children during harvest (HS; n = 320) and pre-harvest season (PHS; n = 312). In addition, 6–12 month old children from the HS were reassessed 6 months later during PHS. In addition to child anthropometry, child feeding practices were collected using 24-h and 7-day dietary recalls. RESULTS: The mean (±SD) length-for-age z-score (LAZ) of the 6–12 month old children was −0.77 (±1.4) and −1.0 (±1.3) in HS and PHS, respectively, while the mean (±SD) of the follow-up children in PHS was −1.0 (±1.3). The median DDS (IQR) was 2.0 (1.0, 3.0.), 2.0 (2.0, 3.0) and 3.0 (2.0, 4.0) for the children in HS, PHS and the follow-up children in PHS, respectively. The DDS in HS was positively associated with LAZ at follow-up (β = 0.16; 95% CI: 0.01, 0.30; P = 0.03) after controlling for confounding factors. ICFI and DDS were not associated with mean LAZ, weight-for-height z-score and weight-for-age z-score within season. However, the odds of being stunted when having a DDS ≤ 2 was 2.3 times (95% CI: 1.10, 4.78; P = 0.03) higher compared to a DDS > 2 child in HS and 1.7 times (95% CI: 1.04, 2.71; P = 0.04) higher for the pooled sample of 6–12 months old children in HS and PHS. CONCLUSIONS: The DDS was found to be an indicator for child stunting during the Ethiopian harvest season. The DDS can be an appropriate tool to evaluate the association of child feeding practices with child growth irrespective of season. Inclusion of other dimensions in the construction of ICFI should be considered in future analysis as we found no association with growth