STRUCTURAL DYNAMICS OF PHOTOLYZED MYOGLOBIN AT LOW TEMPERATURES BY X-RAY ABSORPTION FINE STRUCTURES

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dc.creatorTENG, TSU-YIen_US
dc.date.accessioned2007-05-09T19:46:33Zen_US
dc.date.available2007-05-09T19:46:33Zen_US
dc.date.issued1987en_US
dc.description.abstractX-ray absorption fine structures of photolyzed carboxymyoglobin were measured at 4 K and at 40 K. The latter was a 10-s-resolved measurement following photolysis. The goal of the project was to elucidate the dynamic pathways through which ligand binding couples to protein conformation changes. The project involved five major tasks: (1) We constructed an integration spectrometer for x-ray absorption capable of 100 $\mu$s-resolved measurement. (2) Heme protein samples have to be photolyzable on the one hand and possess a high (Fe) fluorescence yield on the other. This is very difficult to achieve with solution samples. The problem was solved by embedding concentrated $(\sim 10$ mM) myoglobin in thin $(\sim 20\ \mu$m) dry polyvinyl alcohol (PVA) films. Carboxymyoglobin embedded in PVA film, has the same properties as in frozen buffer solution as proven by optical absorption, kinetics of CO recombination following photolysis and x-ray absorption spectra. (3) A cryostat was constructed for x-ray absorption measurement, which was also equipped with optical windows for flash photolysis and optical monitoring of the degree of photodissociation in the sample. (4) Synchrotron radiation experiments were performed at Stanford Synchrotron Radiation Laboratory and at National Synchrotron Light Source at Brookhaven. (5) Data analyses showed that the photolyzed carboxymyoglobin ${\rm (MB\sp\ast)}$ is structurally different from either carboxymyoglobin (MbCO) or deoxymyoglobin (Mb): the Fe-C(O) distance is 1.9 A, 2.17 A, $\infty$ A for MbCO, ${\rm Mb\sp\ast}$ and Mb respectively; the corresponding Fe-${\rm N}\sb{\rm imidazole}$ distances are 2.2 A, 2.18 A, 2.1 A and Fe-${\rm N}\sb{\rm porphyrin}$ distances are 1.97 A, 1.98 A, 2.06 A. At 40 K, from 1 s to 10 s following photolysis, 40% of photodissociated CO has recombined with Fe, and the rest of the sample is indistinguishable from ${\rm Mb\sp\ast}.$ The structure of ${\rm Mb\sp\ast}$ described above is in disagreement with a previous report by Powers et al. (Biochemistry 23, 5519 (1984)).en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.callnoThesis Phys. 1987 Tengen_US
dc.identifier.citationTENG, TSU-YI. "STRUCTURAL DYNAMICS OF PHOTOLYZED MYOGLOBIN AT LOW TEMPERATURES BY X-RAY ABSORPTION FINE STRUCTURES." (1987) Diss., Rice University. <a href="https://hdl.handle.net/1911/16109">https://hdl.handle.net/1911/16109</a>.en_US
dc.identifier.urihttps://hdl.handle.net/1911/16109en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectBiophysicsen_US
dc.titleSTRUCTURAL DYNAMICS OF PHOTOLYZED MYOGLOBIN AT LOW TEMPERATURES BY X-RAY ABSORPTION FINE STRUCTURESen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentPhysicsen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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