Dr.Charles Glabe

Autumn Ivy and John Ycaza

Dr. Randy Villahermosa

Lloyd Ferguson Syposium - Dr. Joseph Francisco

Cecilia Zurita and Valerie Villareal

Alfred Baca and Alex Briseno

Abraham Guerrero and Kandace West

Dr. Steven Dahms


Biomedical Sciences Research Seminars

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MARC-U*STAR Programs

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Biomedical Sciences Seminar Series

Fall 2002 Abstracts
 January 10
January 17


Autumn S. Ivy
(Dr. Amelia Russo-Neustadt)
Oxford Glycobiology Institute, Department of Biochemistry, Oxford University
South Parks Road, OXFORD OX1 3QU, England
(California State University, Los Angeles, 5151 State University Drive, LA, CA 90032)

Pharmacological interventions in mammalian spermatogenesis have involved both hormonal and non-hormonal approaches; however, male contraceptives that do not involve endocrine regulation would be more desirable. Researchers have turned their attention towards glycoconjugates, due to their involvement and expression in spermatogenesis and mature spermatozoa, respectively. It has been recently demonstrated that the oral administration of the imino sugar N-butyldeoxynojirimycin (NB-DNJ) causes reversible infertility in male mice. NB-DNJ is a novel competitive inhibitor of glucosylceramide (GlcCer) synthesis, and has been extensively studied for therapeutic use in the treatment of glycosphingolipid lysosomal storage disorders. In this study, we have characterized both developing spermatids and mature spermatozoa of male mice treated with 15 mg/kg NB-DNJ for five consecutive weeks, to investigate the actual mechanism of involvement of the alkylated imino sugar on male germ cells in causing sterility. Through immunofluorescent labeling and flow cytometry experiments, abnormalities in acrosome and mitochondrial development were observed in drug treated mice. These findings suggest that NB-DNJ could be used as a male contraceptive.

January 24

Phenylene Molecular Wires

Dr. Randy Villahermosa
California Institute of Technology


Electron transfer is an important process in many chemical and biological systems. Photosynthesis, the phenomenon responsible for aerobic life, occurs through a series of well-controlled electron transfer steps. Nature's ability to use chemical structure to modulate electron transfer reactions can serve as a model for developing molecular electronics. Designed to mimic silicon-based electronic components, molecular electronics have the advantage of smaller size and higher bandwidth. In the future, molecular circuits will be made from analogs of transistors, diodes, and data storage units. Molecules that mimic conventional wires will connect the various components of a molecular device and have the added benefits of directionality and tunable conductivity. To gain a better understanding of the science behind molecular electronics, a series of molecular wires based on substituted phenylene oligomers were synthesized. The relationship between the chemical structure of the wires and the measured electron transfer reaction rates was determined using time-resolved laser spectroscopy. Applications of these wires for molecular electronics, solar energy conversion, and enzyme mechanism elucidation will be discussed.

 January 31
 February 7

J.S. Francisco
Joseph S. Francisco

Joseph S. Francisco completed his undergraduate studies in Chemistry at the University of Texas at Austin with honors, and he received his Ph.D. in Chemical Physics at the Massachusetts Institute of Technology in 1983. Francisco spent 1983-1985 as a Research Fellow at Cambridge University in England, and following that he returned to MIT as a Provost Postdoctoral Fellow. In 1986 he was appointed Assistant Professor at Wayne State University. In 1991 he was a Visiting Associate in Planetary Science at California Institute of Technology. He accepted an appointment as Professor of Chemistry and Earth & Atmospheric Sciences at Purdue University in January, 1985. Francisco has received a National Science Foundation Presidential Young Investigator Award, an Alfred P. Sloan Fellowship, and a Camille and Henry Dreyfus Foundation Teacher-Scholar Award. He received the National Organization for the Professional Advancement of Black Chemists and Chemical Engineers Outstanding Teacher Award. In 1993, Francisco was a recipient of a John Simon Guggenheim Fellowship, which he spent at the Jet Propulsion Laboratory at the California Institute of Technology. He received an American Association for the Advancement of Science Mentor Award in 1994. In 1995, he received a Percy L. Julian Award for Pure and Applied Research from the National Organization for the Professional Advancement of Black Chemists and Chemical Engineers. He was a Sigma Xi National Lecturer from 1995 to 1997. He was elected a Fellow of the American Physical Society and a Fellow of the American Association for the Advancement of Science. He was recently awarded an Alexander von Humboldt U.S. Senior Scientist Award by the German government, as well as being appointed a Senior Visiting Fellow at the Institute of Advanced Studies at the University of Bologna, Italy. He has been appointed to and served on committees for the National Research Council, National Science Foundation, and the National Aeronautics and Space Administration. He has been a member of the Naval Research Advisory Committee for the Department of Navy (appointed by the Secretary of the Navy, 1994-1996). He has served as a member of the Editorial Advisory Boards of Spectrochimica Acta Part A and Advances in Environmental Research. He is a co-author of the textbook Chemical Kinetics and Dynamics, published by Prentice-Hall. He has also published over 300 peer-reviewed publications in the fields of atmospheric chemistry, chemical kinetics, quantum chemistry, laser photochemistry and spectroscopy.

 February 14


The Release of Vancomycin Following the Synthesis of Fluoroalkyl
Modified Poly (ethylene glycol)

Ceclia Zurita

Recent studies show that degradable hydrogel systems consisting of end-modified polymers have possible medical applications as drug delivery systems. Current polymers investigated for this purpose, however, liberate the drug at a time scale that is much shorter than desired for long-term controlled release applications. To address this issue, a polymer of polyethylene glycol (PEG) modified with hydrophobic fluoroalkyl segments (-(CH2)2C8F17) = Rf) was tethered to an antibiotic, vancomycin (VAN). It is speculated that this coupling will immobilize the drug within the hydrogel with its release properties dependent on the erosion kinetics of the hydrogel.
Herein hydrophilic PEG chains have been functionalized with two different endgroups, a hydrophobic segment and VAN using a solid state synthesis procedure. A range of techniques including nuclear magnetic resonance (1H-NMR and 19F-NMR), UV-Vis spectrophotometry, high performance liquid chromatography (HPLC), and affinity capillary electrophoresis (ACE) were used to characterize the modified polymers and to study VAN release. Preliminary protein release results indicated a slow release of VAN into a phosphate buffer saline (PBS) supernatant.

Valerie A. Villareal*, Rob G. H. Lammertink, Frank A. Gomez*, Julie A. Kornfield
Dept. of Chemistry & Biochemistry, CSU Los Angeles, Los Angeles, CA 90032* Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125


The use of capillary electrophoresis (CE) and on-column microreactor techniques is a burgeoning area of study. We recently demonstrated the use of CE to study the conversion of nicotinamide adenine dinucleotide (NAD) to nicotinamide adenine dinucleotide reduced form (NADH) in the oxidation of glucose-6-phosphate (glc-6-P) to 6-phosphogluconolactone by glucose-6-phosphate dehydrogenase (G6PDH, EC In this study, multiple plugs of substrate and enzyme are injected separately and allowed to react under electrophoretic conditions. In the present work, we report on the use of injectable self-assembling hydrogels to study the G6PDH reaction. Here, G6PDH is mixed with polyethylene glycol end-capped with fluoroalkyl groups, which aggregate in solution, forming a hydrogel. The formation of the cofactor, NADH and any remaining NAD is monitored by UV detection.



Glucose-6-phosphate Figure6-phosphogluconolactone

Our work indicates G6PDH remains active while in the hydrogel network, thereby greatly reducing the amount of enzyme needed in this simplified biochemical assay.


 February 28

March 7

Phenotypic switch variants of Cryptococcus neoformans differ in gene
expression profile 

A. Guerrero1, N. Jain2, B. Fries2;
1California State University, Los Angeles, CA, 2Albert-Einstein College of
Medicine, Bronx, NY


C. neoformans is a pathogenic yeast, which predominately infects immunocompromised patients. The ATCC C. neoformans strain 24067-RC2 variant is known to undergo phenotypic switching from a parent smooth (SM) colony phenotype to a variant mucoid (MC) colony phenotype in vitro as well as in vivo. Phenotypic switching to MC increases the virulence of the parent SM strain and more importantly changes the outcome of a chronic infection in mice. The switch results in a complex phenotype that involves changes of capsule, cell size, and its capsular polysaccharide. The molecular mechanism that mediates phenotypic switching is unknown. The objective of this study was to identify genes that are involved in phenotypic switching of C. neoformans from a SM to a MC phenotype. We utilized a PCR based differential display approach to identify genes that are differentially expressed during phenotypic switching and may mediate the enhanced virulence. Total RNA was isolated from a stationary culture that was grown 72-hours at 370 and transcribed to cDNA. Primer combinations that yielded a differentially expressed band were repeated with newly transcribed cDNA from a second pool of RNA isolated under the same
conditions. Using 72 primer combinations (approximately 94% coverage), 19 differential expressed bands were confirmed in the second pool of RNA and cloned. These bands were cloned, sequenced, and blasted against the SCTG C.neoformans genome database and the Oklahoma cDNA C. neoformans database. Out of all the genes eight were identified by real time PCR to be differentially regulated between SM and MC. Most importantly, all of the genes are unknown to date and 7 are up-regulated in the SM switch variant relative to the MC variant. We conclude that i.) Phenotypic switch variants exhibit differential gene expression. ii.) Our data suggests that the switch from SM to MC involves a down regulation of genes in MC. iii.) We propose that some of these genes
will include new virulence genes. Ongoing studies are directed to clone and functionally characterize the role of these differentially expressed genes in phenotypic switching.

March 14
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