Molecular flexibility of citrus pectins by combined sedimentation and viscosity analysis

The flexibility/rigidity of pectins plays an important part in their structure-function relationship and therefore on their commercial applications in the food and biomedical industries. Earlier studies based on sedimentation analysis in the ultracentrifuge have focused on molecular weight distributions and qualitative and semi-quantitative descriptions based on power law and Wales-van Holde treatments of conformation in terms of "extended" conformations [Harding, S. E., Berth, G., Ball, A., Mitchell, J.R., & Garcìa de la Torre, J. (1991). The molecular weight distribution and conformation of citrus pectins in solution studied by hydrodynamics. Carbohydrate Polymers, 168, 1-15; Morris, G. A., Foster, T. J., & Harding, S.E. (2000). The effect of degree of esterification on the hydrodynamic properties of citrus pectin. Food Hydrocolloids, 14, 227-235]. In the present study, four pectins of low degree of esterification 17-27% and one of high degree of esterification (70%) were characterised in aqueous solution (0.1 M NaCl) in terms of intrinsic viscosity [η], sedimentation coefficient (s°20,w) and weight average molar mass (Mw). Solution conformation/flexibility was estimated qualitatively using the conformation zoning method [Pavlov, G.M., Rowe, A.J., & Harding, S.E. (1997). Conformation zoning of large molecules using the analytical ultracentrifuge. Trends in Analytical Chemistry, 16, 401-405] and quantitatively (persistence length Lp) using the traditional Bohdanecky and Yamakawa-Fujii relations combined together by minimisation of a target function. Sedimentation conformation zoning showed an extended coil (Type C) conformation and persistence lengths all within the range Lp=10-13 nm (for a fixed mass per unit length)

Determining the generality of preference assessment outcomes across prices

Paired-stimulus preference assessments are a common way for behavior analysts to identify items to use as reinforcers with their clients (Graff & Karsten, 2012). These assessments are conducted at low schedule values but items identified are often used clinically at higher ratio requirements and expected to maintain the same level of reinforcing efficacy

Therapeutic Experience of Maximum Feasible Participation

"Indigeneity at the Crossroads of American Studies." Published as a special joint issue with American Studies, Volume 46, No. 3/4, Fall 2005

The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs

The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu134 in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu134- and Gln134-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface

The effects of music on students' on task behavior

Middle School math students performed their typical daily math classwork with and auditory environment of either teacher chosen music, student chosen music played through individual headphones, or silence. One day each week during a six week summer session was dedicated to each of the three listening options. On the additional two days, students were free to work with headphones or in the normal classroom noise level, according to school and classroom rules. The students were attending a segregated school for students with learning differences. Their on task behavior was observed and recorded three times during each class period. Teacher selected music consisted of a mix of classical music and world music genres. Students were found to be more focused on their work when music was being played as compared to a silent environment. Key words: music, focus, special education, attention, distractio

Surveillance and identity: conceptual framework and formal models

Surveillance is recognised as a social phenomenon that is commonplace, employed by governments, companies and communities for a wide variety of reasons. Surveillance is fundamental in cybersecurity as it provides tools for prevention and detection; it is also a source of controversies related to privacy and freedom. Building on general studies of surveillance, we identify and analyse certain concepts that are central to surveillance. To do this we employ formal methods based on elementary algebra. First, we show that disparate forms of surveillance have a common structure and can be unified by abstract mathematical concepts. The model shows that (i) finding identities and (ii) sorting identities into categories are fundamental in conceptualising surveillance. Secondly, we develop a formal model that theorizes identity as abstract data that we call identifiers. The model views identity through the computational lens of the theory of abstract data types. We examine the ways identifiers depend upon each other; and show that the provenance of identifiers depends upon translations between systems of identifiers