This dissertation describes a tight-binding technique that treats the dynamics of electrons and ions simultaneously. The main features are a generalized Hellmann- Feynman theorem, a standard, time-dependent, self-consistent-field description and the interaction picture. The time-dependence is incorporated by using Peierls Substitution. We also apply the velocity-Verlet algorithm to predict the motion of the ions. We first test the validity of this semi-empirical tight-binding approach on several smaller systems including ethylene, 2-butene, and stilbene. The cis-trans isomerization is modeled and in each case the results agree well with those obtained from other computational and empirical methods. Next, we use the tight-binding model to simulate the photoisomerization of the retinal molecule from its cis to trans form. The results are comparable to those obtained from experiments. The vibrational frequencies for retinal obtained using the force-constant techniques in this model agree well with those obtained from Fourier transform methods and a standard software. The cis-trans isomerization takes 217.91 fs to complete with a field strength of 1.0 gauss·cm, which is comparable to 200 fs reported from experiments. The isomerization depends on the strength of the vector potential, the time-step of the simulation and also the wavelength of the light. Using different parameters the isomerization takes place in 1-2 ps which is within the range reported from experimentation. The present semi-empirical technique provides an excellent compromise between computationally-prohibitive first principles methods and approximate empirical methods to model the motion of electrons and ions in a large molecule like retinal.

by Xu Xun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 78-87). / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter CHAPTER 2 --- LITERATURE REVIEW --- p.6 / Chapter 2.1 --- Anatomy of retina and vitreous --- p.6 / Chapter 2.2 --- Rhegmatogenous retinal detachment --- p.8 / Chapter 2.2.1 --- Retinal breaks --- p.8 / Chapter 2.2.2 --- Retinal detachment and subretinal fluid --- p.8 / Chapter 2.3 --- Proliferative vitreoretinopathy --- p.9 / Chapter 2.4 --- Total protein in subretinal fluid --- p.11 / Chapter 2.5 --- Fibroblast growth factor --- p.12 / Chapter 2.5.1 --- Structure of b and a FGF and their gene --- p.13 / Chapter 2.5.2 --- Expression of bFGF and aFGF in neuroretinal and pigment epithelial cells --- p.14 / Chapter 2.5.3 --- The FGF receptors --- p.15 / Chapter 2.5.4 --- In vitro biological effect of FGF --- p.15 / Chapter 2.5.5 --- FGF in retinal diseases --- p.16 / Chapter 2.6 --- Cellular study of proliferative vitreoretinopathy --- p.18 / Chapter 2.6.1 --- Experimental study --- p.18 / Chapter 2.6.2 --- Pathogenesis of intravitreal proliferation --- p.20 / Chapter 2.6.3 --- Cellular components of proliferative tissue --- p.20 / Chapter 2.6.4 --- Cellular components of subretinal fluid --- p.22 / Chapter CHAPTER 3 --- MATERIALS AND METHODS --- p.24 / Chapter 3.1 --- Specimens --- p.24 / Chapter 3.2 --- Determination of total protein --- p.24 / Chapter 3.2.1 --- Study population --- p.24 / Chapter 3.2.2 --- Quantitation of total protein --- p.25 / Chapter 3.3 --- Determination of bFGF --- p.27 / Chapter 3.3.1 --- Study population --- p.27 / Chapter 3.3.2 --- Quantitation of bFGF --- p.28 / Chapter 3.4 --- Celular study --- p.30 / Chapter 3.4.1 --- Study population --- p.30 / Chapter 3.4.2 --- Fixation of samples --- p.30 / Chapter 3.4.3 --- Immunocytology --- p.32 / Chapter 3.4.4 --- Examination of autofluorescence --- p.35 / Chapter 3.4.5 --- Hematoxylin and eosin staining --- p.36 / Chapter CHAPTER 4 --- RESULTS --- p.37 / Chapter 4.1 --- Total protein --- p.37 / Chapter 4.1.2 --- Total protein in subretinal fluids --- p.38 / Chapter 4.1.3 --- Total protein in normal vitreous of autopsy and sera of patients --- p.40 / Chapter 4.1.4 --- Relationship of protein level and size of retinal break --- p.40 / Chapter 4.1.5 --- Relationship of protein level and duration of retinal detachment --- p.43 / Chapter 4.1.6 --- Relationship of protein level and degree of PVR --- p.45 / Chapter 4.2 --- Basic FGF in subretinal fluids --- p.47 / Chapter 4.2.1 --- Standard curve for determination of bFGF in SRF --- p.47 / Chapter 4.2.2 --- The levels of bFGF in both SRF and controls --- p.48 / Chapter 4.2.3 --- Levels of bFGF in different degrees of PVR --- p.50 / Chapter 4.2.4 --- Levels of bFGF in SRF of RD with and without previous cryotherapy --- p.54 / Chapter 4.2.5 --- The relationship of level of protein and bFGF --- p.55 / Chapter 4.3 --- Results of cytological examination --- p.57 / Chapter 4.3.1 --- Pigment examingnation by autofluorescence --- p.57 / Chapter 4.3.2 --- Cellular study of subretinal fluids --- p.59 / Chapter 4.3.3 --- Cellular study of subretinal fluid in eyes with prior cryotherapy --- p.62 / Chapter CHAPTER 5 --- DISCUSSION --- p.68 / Chapter 5.1 --- Evaluaton of method for obtaining specimens --- p.68 / Chapter 5.2 --- Total protein of SRF in retinal detachment --- p.69 / Chapter 5.3 --- Basic FGF in subretinal fluids --- p.71 / Chapter 5.4 --- Elevated level of bFGF in eye after cryotherapy --- p.74 / Chapter 5.5 --- Cell components in SRF of PVR --- p.75 / REFERENCES --- p.78

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

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