Osman Koroma

University of Milan, Italy 2018 - 2021

Field of study: Pharmacology and Biomolecular Sciences
Degree: MSc in Safety Assessment of Xenobiotics and Biotechnological Products

Antioxidant and cell protective effects of delphinidin and delphinidin-containing plant derived products

I focus my attention on the antioxidant activity of the anthocyanidine Delphinidin, as well as of Maqui berry (MBE) and Blueberry (BBC), which are rich in anthocyanidine. These substances are tested in the Ferric Reductive Activity Potential (FRAP) assay and the total phenolic content is measured. To investigate the protective effect of Delphinidin, MBE and BBC, Human lymphoblastoid TK6 cells were treated with the genotoxic compound Methyl Methane Sulfonate (MMS). The addition of the cytokinesis inhibitor yield formation of double- or multinucleated cells, which can be quantified to calculate a proliferation index as sensitive marker for cytotoxic or cytostatic effects. Finally, genotoxicity experiments were performed. The endpoint for detection of genotoxicity is micronucleus formation, which represents a type of chromosomal aberrations.

In this work, Delphinidin, MBE and BBC were evaluated to better understand their possible ability to protect cells from the micronucleus inducing activity of MMS. Since anthocyanidine are often bound to sugars as glycosides in plants and such glycosides are not able to enter mammalian cells, a hydrolysis step to release the anthocyanidine from their sugar-binding is performed on MBE and BBC and the protective effects are compared between original and hydrolyzed MBE and BBC.

Njala University 2011 - 2016

Field of study: Environmental Chemistry
Degree: Bsc(HONS) Environmental Chemistry

 PRODUCTION AND PURIFICATION OF CARDIAC PACEMAKER CHANNEL (HCN4)
FOR CRYO-EM STRUCTURAL STUIDES

I focused my attention on the HCN4 isoform, which is the predominant HCN channel
isoform expressed in the heart and thus the major determinant of the cardiac pacemaker HCN
current (If). HCN4 is a particularly attractive candidate for addressing unresolved questions
regarding the cAMP pathway. Unlike HCN1 channels, HCN4 channels show a very large
response to cAMP, the largest among HCN isoforms.
In this work, I set the conditions for large-scale expression of HCN4 channel protein in Human
Embryonic Kidney HEK293F cell line for its subsequent purification by using several membrane
mimetic environments: detergents, amphipols and nanodiscs. Thermal denaturation assay was
used to investigate the stability of purified HCN4 protein in the different membrane mimics. The
ultimate goal of the production and purification of HCN4 channel protein is to prepare good
specimens for cryo-Electron Microscopy (cryo-EM), a spectroscopic technique already
successfully employed to solve HCN1 structures. Moreover, I used Thermal denaturation to detect
binding of cAMP to the purified HCN4 protein. To the best of my knowledge, this is the first
example of ligand binding detected on the purified full-length HCN channels. The proof of
concept of cAMP binding to purified HCN4 channels will open to the possibility of monitoring
binding of pharmacologically relevant drugs to this ion channel family