Dengue fever has re-emerged as a global health risk over the past 10 years. The Dengue virus is transmitted by the Aedes aegypti mosquito, which becomes infected with the virus upon blood feeding on an infected human host. Blood feeding, and hence blood meal digestion, is required to obtain the proper nutrients for completion of the gonotrophic cycle. Serine proteolytic enzymes digest the blood meal proteins, and although there are functional studies that have demonstrated the important roles these serine proteases play in blood meal metabolism, no one has biochemically characterized these proteases in vitro. I have engineered recombinant protease constructs that enable us to express, purify, and activate mosquito proteases in vitro using a bacterial expression system and a denaturation/refolding strategy. The four major midgut proteases studied (AaET, AaLT, AaSPVI, and AaSPVII), were purified to near homogeneity and were shown to be active in in vitro enzyme assays. Kinetic parameters, using the artificial trypsin substrate BApNA, were determined for three of the four mosquito proteases. AaLT, which was originally believed to be the major trypsin involved in blood meal digestion in the later phase portion of digestion, was shown not to be a classic trypsin based on in vitro BApNA assays. However, this same AaLT enzyme preparation was shown to cleave natural blood meal protein substrates (serum albumin and hemoglobin), confirming its proteolytic activity. Determination of mosquito protease activities and partial proteolysis of bovine serum albumin (BSA) provide evidence that the four proteases have selective cleavage sites. We also present initial evidence that mosquito proteases may be autocatalytic, based on in vitro auto-cleavage assays with AaET and AaLT.

<p> A Langmuir film, which is a molecularly thin insoluble film on a liquid substrate, is one practical realization of a quasi-two dimensional matter. The major advantages of this system for the study of phase separation and phase co-existence are (a) it allows accurate control of the components and molecular area of the film and (b) it can be studied by various methods that require very flat films. </p><p> Phase separation in molecularly thin films plays an important role in a range of systems from biomembranes to biosensors. For example, phase-separated lipid nano-domains in biomembranes are thought to play crucial roles in membrane function. I use Brewster Angel Microscopy (BAM) coupled with Fluorescence Microscopy (FM) and static Light Scattering Microscopy (LSM) to image phases and patterns within Langmuir films. The three microscopic techniques &mdash; BAM, FM and LSM &mdash; are complimentary to each other, providing distinct sets of information. They allow direct comparison with literature results in lipid systems. </p><p> I have quantitatively validated the use of detailed hydrodynamic simulations to determine line tension in monolayers. Line tension decreases as temperature rises. This decrease gives us information on the entropy associated with the line, and thus about line structure. I carefully consider the thermodynamics of line energy and entropy to make this connection. In the longer run, LSM will be exploited to give us further information about line structure. I have also extended the technique by testing it on domains within the curved surface of a bilayer vesicle. I also note that in the same way that the presence of surface-active agents, known as surfactants, affects surface energy, the addiction of line active agents alters the inter-phase line energy. Thus my results set to stage to systematically study the influence of line active agents &mdash;'linactants' &mdash; on the inter-phase line energy. </p><p> Hierarchal self-assembled chiral patterns were observed as a function of temperature. I found that the appearance of these domains could be explained with a simple uniaxial optical axis in the underlying structure, which is the first critical step to understanding the origin of these patterns.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0832. Adviser: Taekjip Ha. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of California, San Francisco, 2007. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0830. Adviser: David A. Agard.

Thesis (Ph.D.)--Indiana University, Dept. of Physics, 2007. / Title from dissertation home page (viewed Sept. 29, 2008). Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0881. Adviser: James A. Glazier.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 71-02, Section: B, page: . Adviser: David A. Agard.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 5988. Adviser: Alan D. Frankel.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 6049. Adviser: Robert M. Stroud.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6474. Adviser: Enrico Gratton. Includes bibliographical references (leaves 98-111). Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6250. Adviser: Taekjip Ha. Includes bibliographical references (leaves 114-119) Available on microfilm from Pro Quest Information and Learning.