Publication Date

2018-12-05

Availability

Open access

Embargo Period

2018-12-05

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Chemistry (Arts and Sciences)

Date of Defense

2018-10-31

First Committee Member

Roger M. Leblanc

Second Committee Member

Francisco M. Rayomo

Third Committee Member

Jamie D. Walls

Fourth Committee Member

Jean-Marie A. Parel

Abstract

The content of this thesis is an investigation into physicochemical, photophysical, and interfacial properties of β-galactosidase, a crucial enzyme, its conjugate with CDs, interaction of β-galactosidase with X-gal, and surface chemistry and spectroscopic study of toxins, Cholera toxin B (CTB) and Fumonisin B1 (FB1). The objective of the work was to understand the surface chemistry behavior of the important enzyme, conjugates and toxins in a model systems representing vaguely cell membrane environments, to prove the activity of the deposited enzyme, its conjugate, and toxins in a form of the monolayer. We also studied the effect of green LED light on the FB1 Langmuir monolayer which will be useful for possible future treatment of fungal keratitis without any side effects. Furthermore, this approach can be employed to understand the property of transmembrane receptors, to study the cell adhesion, and its implications. Besides that, this information is relevant for the successful deposition of Langmuir-Blodgett (LB) film. The Langmuir monolayer isotherm of enzyme, conjugate and the toxin were studied using the surface chemistry and spectroscopy at the air-water/subphase interphase. We employed the pressure (π)-area (A) isotherm measurement which is typically the very first step in the study of these enzymatic and non-enzymatic molecules floating at the subphase surface as it gives useful information on the existence of different phases, phase transitions and the stability of Langmuir monolayer at fixed temperature and pH. During our study we found that β-galactosidase as well as its conjugate form stable Langmuir monolayer. We observed that during the interaction of the enzyme with X-gal, its secondary structure changes. This does not mean that the overall structure of the enzyme gets changed. This is because enzyme structure is determined by primary, secondary, tertiary, and quaternary structure. The interfacial study of CTB showed that the molecule is very stable at the air-subphase interface. In performing surface chemistry and spectroscopic study of FB1 molecule, the interesting finding that came out of the FB1 Langmuir monolayer investigation was that the analyte adopted stability (without irradiation of green LED light) at the monolayer and remained degraded with subsequent effect of the green LED light (525 nm) at air-water interface.

Keywords

β-galactosidase; Conjugate; Cholera toxin B; Langmuir Monolayer; Fumonisin B1

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