Managing Tortillas, Pitas, Matzo, and Mano when you Grew up on White Bread

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Deaf and Hearing: Conducting Cross-Cultural Research in a Postsecondary Setting

This paper describes cross-cultural research methods that were used in a case study of a community college in the Midwest. During the course of the research, the importance of applying cross-cultural research methods became apparent. Analysis of the research process resulted in a identification of three aspects of cross-cultural design. These are the cross cultural research guidelines applied to Deafness, the context of the study, and the conduct of the research. The results indicated that when the interests of people who were Deaf were considered, cross-cultural collaboration was possible, there was benefit to the Deaf culture and the mainstream, and professionals who were Deaf were recognized

Measuring Angular Rate of Celestial Objects Using the Space Surveillance Telescope

To date, much effort has been spent on improving the detection of space objects; however, the ability to track and catalogue space objects remains only as good as the ability to determine the object\u27s position and angular rate. The foundation of space situational awareness (SSA) is the ability to detect a space object and to predict its location in the future. In order to accomplish SSA for Geosynchronous Earth Orbit (GEO) space objects, the Defense Advanced Research Projects Agency (DARPA) developed the Space Surveillance Telescope (SST) to enable ground-based, broad-area search, detection and tracking of small GEO objects in space. In general, the SST tracks along the sky at the sidereal rate where the stars will appear to be stationary, while objects within space not moving at this rate will appear to move across the focal array from data frame to data frame. As the time between each frame is known and the position of the detected object can be determined in the focal array, it is possible to measure the angular position and angular rate of a detected object. The two main types of detection algorithms used in this thesis are the binary hypothesis test (BHT) and the multi-hypothesis test (MHT), which both rely on a log-likelihood ratio (LLR); however, the MHT algorithm adds an additional step to correlate nine system point spread functions, or hypotheses, with the image data. These detection algorithms lead to varying degrees of accuracy and precision in determining the position and angular rate for a detected space object. The research within this thesis shows that the MHT algorithm is more accurate and precise than the BHT algorithm

Differential Hydrogen Bonding in Human CYP17 Dictates Hydroxylation versus Lyase Chemistry

Consequences of alternative H-bonding: Raman spectra of oxygenated intermediates of Nanodisc-incorporated human CYP17 in the presence of natural substrates (pregnenolone and progesterone) directly confirm that substrate structure effectively alters hydrogen-bonding interactions with the critical Fe–O–O fragment and dictates its predisposition for one of two alternative reaction pathways. Such substrate control has profound physiological implications

Resonance Raman Spectroscopy of the Oxygenated Intermediates of Human CYP19A1 Implicates a Compound I Intermediate in the Final Lyase Step

CYP19A1, or aromatase, a cytochrome P450 responsible for estrogen biosynthesis in humans, is an important therapeutic target for the treatment of breast cancer. There is still controversy surrounding the identity of reaction intermediate that catalyzes carbon–carbon scission in this key enzyme. Probing the oxy-complexes of CYP19A1 poised for hydroxylase and lyase chemistries using resonance Raman spectroscopy and drawing a comparison with CYP17A1, we have found no significant difference in the frequencies or isotopic shifts for these two steps in CYP19A1. Our experiments implicate the involvement of Compound I in the terminal lyase step of CYP19A1 catalysis

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Resonance Raman Spectroscopy Reveals that Substrate Structure Selectively Impacts the Heme-Bound Diatomic Ligands of CYP17

An important function of steroidogenic cytochromes P450 is the transformation of cholesterol to produce androgens, estrogens, and the corticosteroids. The activities of cytochrome P450c17 (CYP17) are essential in sex hormone biosynthesis, with severe developmental defects being a consequence of deficiency or mutations. The first reaction catalyzed by this multifunctional P450 is the 17α-hydroxylation of pregnenolone (PREG) to 17α-hydroxypregnenolone (17-OH PREG) and progesterone (PROG) to 17α-hydroxyprogesterone (17-OH PROG). The hydroxylated products then either are used for production of corticoids or undergo a second CYP17 catalyzed transformation, representing the first committed step of androgen formation. While the hydroxylation reactions are catalyzed by the well-known Compound I intermediate, the lyase reaction is believed to involve nucleophilic attack of the earlier peroxo- intermediate on the C20-carbonyl. Herein, resonance Raman (rR) spectroscopy reveals that substrate structure does not impact heme structure for this set of physiologically important substrates. On the other hand, rR spectra obtained here for the ferrous CO adducts with these four substrates show that substrates do interact differently with the Fe-C-O fragment, with large differences between the spectra obtained for the samples containing 17-OH PROG and 17-OH PREG, the latter providing evidence for the presence of two Fe-C-O conformers. Collectively, these results demonstrate that individual substrates can differentially impact the disposition of a heme-bound ligand, including dioxygen, altering the reactivity patterns in such a way as to promote preferred chemical conversions, thereby avoiding the profound functional consequences of unwanted side reactions

Unveiling the Crucial Intermediates in Androgen Production

Significance: The human enzyme cytochrome P450 17A1 (CYP17A1) catalyzes the critical step in the biosynthesis of the male sex hormones, and, as such, it is a key target for the inhibition of testosterone production that is necessary for the progression of certain cancers. CYP17A1 catalyzes two distinct types of chemical transformations. The first is the hydroxylation of the steroid precursors pregnenolone and progesterone. The second is a different reaction involving carbon–carbon (C-C) bond cleavage, the mechanism of which has been actively debated in the literature. Using a combination of chemical and biophysical methods, we have been able to trap and characterize the active intermediate in this C-C lyase reaction, an important step in the potential design of mechanism-based inhibitors for the treatment of prostate cancers. Abstract: Ablation of androgen production through surgery is one strategy against prostate cancer, with the current focus placed on pharmaceutical intervention to restrict androgen synthesis selectively, an endeavor that could benefit from the enhanced understanding of enzymatic mechanisms that derives from characterization of key reaction intermediates. The multifunctional cytochrome P450 17A1 (CYP17A1) first catalyzes the typical hydroxylation of its primary substrate, pregnenolone (PREG) and then also orchestrates a remarkable C17–C20 bond cleavage (lyase) reaction, converting the 17-hydroxypregnenolone initial product to dehydroepiandrosterone, a process representing the first committed step in the biosynthesis of androgens. Now, we report the capture and structural characterization of intermediates produced during this lyase step: an initial peroxo-anion intermediate, poised for nucleophilic attack on the C20 position by a substrate-associated H-bond, and the crucial ferric peroxo-hemiacetal intermediate that precedes carbon–carbon (C-C) bond cleavage. These studies provide a rare glimpse at the actual structural determinants of a chemical transformation that carries profound physiological consequences

Defining CYP3A4 Structural Responses to Substrate Binding. Raman Spectroscopic Studies of a Nanodisc-incorporated Mammalian Cytochrome P450

Resonance Raman (RR) spectroscopy is used to help define active site structural responses of nanodisc-incorporated CYP3A4 to the binding of three substrates: bromocriptine (BC), erythromycin (ERY), and testosterone (TST). We demonstrate that nanodisc-incorporated assemblies reveal much more well-defined active site RR spectroscopic responses as compared to those normally obtained with the conventional, detergent-stabilized, sampling strategies. While ERY and BC are known to bind to CYP3A4 with a 1:1 stoichiometry, only the BC induces a substantial conversion from low- to high-spin state, as clearly manifested in the RR spectra acquired herein. The third substrate, TST, displays significant homotropic interactions within CYP3A4, the active site binding up to 3 molecules of this substrate, with the functional properties varying in response to binding of individual substrate molecules. While such behavior seemingly suggests the possibility that each substrate binding event induces functionally important heme structural changes, up to this time spectroscopic evidence for such structural changes has not been available. The current RR spectroscopic studies show clearly that accommodation of different size substrates, and different loading of TST, do not significantly affect the structure of the substrate-bound ferric heme. However, it is here demonstrated that the nature and number of bound substrates do have an extraordinary influence on the conformation of bound exogenous ligands, such as CO or dioxygen and its reduced forms, implying an effective mechanism whereby substrate structure can impact reactivity of intermediates so as to influence function, as reflected in the diverse reactivity of this drug metabolizing cytochrome