Biomedical Sciences

Permanent URI for this collection

https://hdl.handle.net/10323/11884

Browse

Browsing Biomedical Sciences by Author "Madlambayan, Gerard"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Discrete Functionalization of Resorcinarenes for Applications in Supramolecular Chemistry
    (2023-01-01) Twum, Kwaku; Beyeh, Ngong K.; Sevilla, Michael; Yang, Ziming; Madlambayan, Gerard
    Resorcinarenes are three-dimensional cyclic oligomers obtained by acid-catalyzed condensation between resorcinol and an appropriate aldehyde. This doctoral thesis research presents basic and translational research studies that demonstrate the versatile functionalization and applications of the resorcinarene macrocycle. In chapter one, this thesis introduces macrocyclic chemistry with a brief reflection on the history of the science and Beyeh Lab’s use of the resorcinarene macrocycle in supramolecular chemistry. Chapter two presents a fundamental study of cooperativity in non-covalent interactions using a resorcinarene as an anchor to a guest in a solution that restricts its free rotation in the solution. Chapter three explores the molecular recognition potential of functionalized resorcinarenes as sensors for ammonium cations and pyrophosphate anions. Last, chapter four presents functionalized water-soluble resorcinarenes as aggregation inhibitors for peptides that cause eye cataracts. These applications are all realized through the persistent hydrophobic cavity inherent in the basic resorcinarene cavitand and the synthetic functionalization of the macrocyclic ring, which underscores the versatile use of resorcinarene compounds in supramolecular chemistry.
  • Thumbnail Image
    Item
    Phosphorylation Patterns, Aggregation Propensities, and Morphological Studies of The Various Tau Protein Isoforms
    (2022-03-25) Laryea, Erving Torgbor; Wu, Colin; Avery, Adam; Madlambayan, Gerard
    Tau protein is a microtubule-binding protein as well as a biomarker of neurodegeneration. Its core function is to stabilize microtubules for proper neuronal communication. When hyperphosphorylated, it detaches itself from microtubules and self-assembles into cytotoxic structures. However, little is known about how phosphorylation, the commonest posttranslational modification process found in eukaryotic cells regulate Tau protein structure, conformation, and function. Herein, the role of specific kinases or kinase combinations from the three main classes of proteins kinases that phosphorylate Tau: Proline-directing protein kinase (Glycogen synthase kinase (GSK-3β)) and non-proline directing protein kinase (Microtubule associated regulating kinase (MARK4)) and Tyrosine kinase (Fyn) were systematically evaluated in vitro. After the expression and purification of all the six Tau isoforms from E. Coli cells, Tau 441, also known as full-length Tau, which comprises of all the domains found in the other isoforms was extensively investigated. Phosphorylation of Tau 441 by GSK-3β, MARK4 and Fyn was detected by immunostaining using phosphospecific antibodies. With Tau protein been identified to co-localize with sulfated aminoglycans such as heparin and heparin sulfates, single and multi-kinase phosphorylated aggregation studies of Tau 441 were conducted in the presence or absence of heparin. Functional assays including proteostat assays, turbidity assays and SDS-PAGE were used to evaluate the aggregation properties of Tau 441 after phosphorylation.The phosphosites on all the single and multi-kinase phosphorylated Tau 441 samples were characterized by Tandem mass spectrometry. Tau 441 protein structure and conformational changes after phosphorylation was also determined by Hydrogen Deuterium Exchange mass spectrometry (HDX-MS). The flexibility and accessibility to the first and second hexapeptide repeats (H1 and H2), a repeat motif found in the MTBR of Tau protein identified to increase the aggregation tendencies of Tau protein were used to describe the single kinase or multi-kinase combinations evaluated ability to promote Tau fibrillization.
  • Thumbnail Image
    Item
    The Role of CD49f - Integrin α6- in Human Stem Cell Biology
    (2021-11-15) Timilsina, Suraj; Villa-Diaz, Luis; K. Lal, Shailesh; Madlambayan, Gerard
    Owing to the intrinsic capability for unlimited self-renewal and the ability to make all the cells in the body, pluripotent stem cells (PSC) are an ideal candidate to be used as starting material for cell therapies. The development of a standard human PSC (hPSC), which includes embryonic stem cells (hESC) and induced pluripotent stem cells (hiPSC), culture methods using completely defined and xeno-free culture environment will advance our knowledge of hPSC biology, and also increase the effectiveness of hPSC expansion on defined conditions for potential human applications. It has been shown that stem cell fates are controlled by their specialized microenvironment, the stem cell niche, via direct cell-cell interactions, cell-extracellular matrix (ECM) contact- largely by surface proteins known as integrins- and the molecular signals emitting from the niche. Activation of integrins by binding to their ligands triggers signal transduction mechanisms involved in cell fate determination. In addition, because of their cell surface localization, integrins are used as biological markers to identify cell populations, and in this regard, integrin α6 (ITGA6), also known as CD49f, is a key biomarker identifying stem cells as it is commonly expressed in all identified stem cell types. Although, numerous findings strongly suggest that CD49f plays important functions in stem cell biology, the underlying molecular mechanisms by which CD49f sustain stem cell’s self-renewal have been only partially described. In this project I have established a chemically defined and xeno-free culture condition for long-term maintenance and derivation of hPSC using chemically defined and xeno-free culture conditions. I also described a novel molecular mechanism involved in the maintenance of self-renewal and proliferation of hPSC using simulated microgravity (sμg). Moreover, my results highlighted CD49f as a reliable biomarker in identifying and characterizing functional status of human mesenchymal stem cells (hMSC).