Thesis (Ph. D.)--University of Florida, 1982. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 152-156).

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Title from PDF t.p. (viewed July 21, 2010). Includes bibliographical references (p. 72-74).

Thesis (Ph. D. in Biomedical Engineering)--Vanderbilt University, Dec. 2006. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Canterbury, 2005. / Typescript (photocopy). Includes bibliographical references (leaves 140-159). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 103-108). Also available for download via the World Wide Web; free to University of Oregon users.

No description available.

Στην παρούσα μεταπτυχιακή αυτή εργασία μελετήσαμε την συμπεριφορά για πρώτη φορά ενώσεων που είχαν σαν βάση την βενζοδισθιαζόλη. Συγκεκριμένα οι ενώσεις αυτές μελετήθηκαν με την χρήση των τεχνικών της φασματοσκοπίας διφωτονικής απορρόφησης της φασματοσκοπίας σταθερής κατάστασης και της φασματοσκοπίας φθορισμού χρονικής ανάλυσης. Αρχικά όσον αφορά την φασματοσκοπία διφωτονικής απορρόφησης, μπορέσαμε να οδηγηθούμε στα εξής συμπεράσματα: οι καλύτερες ενώσεις που παρουσιάζουν αρκετά μεγάλη διφωτονική απορρόφηση είναι τα γραμμικά μόρια (PK-439 και PK-452) σε σχέση με τα U-shaped μόρια με μέγιστη ενεργό διατομή ΔΦΑ ~2000GM. Επιπλέον παρατηρήσαμε ότι η χρήση της βενζοδισθιαζόλης σαν κεντρικός πυρήνας προκαλεί σημαντική αύξηση της διφωτονικής απορρόφησης, σε σχέση με την βενζοθιαζόλη. Τέλος, με την τεχνική της φασματοσκοπίας φθορισμού χρονικής ανάλυσης μπορέσαμε να οδηγηθούμε σε κάποιες διαπιστώσεις: συγκεκριμένα παρατηρήσαμε ότι όσο το μήκος κύματος καταγραφής μεγαλώνει, τόσο οι καμπύλες αποδιέγερσης γίνονται πιο αργές. Ακόμα διαπιστώσαμε ότι από την σύγκριση μορίων στο μήκος κύματος του μεγίστου, σε εκείνα τα μόρια που αποδιεγείρονται γρήγορα, ευνοούνται οι μη-ακτινοβολητικές διεργασίες και ταυτόχρονα παρουσιάζουν μικρή ενεργό διατομή ΔΦΑ. / --

Call number: LD2668 .T4 1979 H83 / Master of Science

Submitted in complete fulfilment for Masters Degree in Technology: Biotechnology, Durban University of Technology, 2013. / A comparative thermostability analysis of different partially purified xylanases from Rhodothermus marinus, Bacillus halodurans, Thermomyces lanuginosus and Pulpzyme HC was studied using differential scanning fluorometry (DSF), fluorescence spectroscopy and circular dichroism (CD). The R. marinus xylanase was found to have an optimum temperature and pH of 90oC and 6 respectively while the B. halodurans xylanase was optimally active at 70oC and a broad range of alkaline pH of 8 - 10. The commercially available xylanase from T. lanuginosus showed optimal activity at 50oC and pH 7 while the Novozyme xylanase Pulpzyme HC showed optimal activity at 60oC and pH 7. Fluorescence spectroscopy monitored the microenvironment and fluorescence emission of Trp residues. In their native folded state, Trp are generally located in the core of the protein but during unfolding they become exposed. The fluorescence changes as the enzyme undergoes denaturation due to conformational changes and exposure of Trp residues. Differential scanning fluorometry (DSF) monitors thermal unfolding of proteins in the presence of a fluorescent dye such as Spyro Orange. A wide range of buffers were tested for their ability to increase the xylanase stability. T. lanuginosus had the greatest increase in melting temperature with 0.73M Bis Tris pH 6.5 and peaked highest at 78°C. The B. halodurans xylanase exhibited high pH stability (pH 4-10) and exhibited very little change in melting temperature, from 74°C-77°C over the twenty four different conditions. The R. marinus xylanase had no increase in melting temperature showing a maximum melting temperature of 90oC. Circular dichroism (CD) measures unequal absorption of right- and left-handed circularly polarized light by the molecule. The xylanase from R. marinus exhibited the lowest ΔG of 34.71kJ at 90°C as was expected. The B. halodurans xylanase showed a much higher ΔG of -52.71 at its optimum temperature of 70°C when compared with the xylanases from R. marinus and T. lanuginosus. When comparing the three xylanases activities at 70°C, it can be seen that the B. halodurans xylanase exhibited a lower relative activity then both R. marinus and T. lanuginosus xylanases. All three techniques offered different information on the structure and function relationship. Fluorescence spectroscopy, the change in conformation due to fluorescence emission as a result of increased temperature and salt concentrations. DSF, optimal conditions for increased stability and activity at higher temperatures and CD, conformational changes, the fraction of folded protein and change in Gibbs free energy over a range of temperature. / National Research Foundation