This study explores changes in assessment patterns in honors organic chemistry exams at the University of Cape Town. By adapting Bloom's taxonomy, we developed a detailed workflow for coding exam questions in order to map cognitive distributions and reveal patterns in assessment focus over a 10-year period. Our findings show significant shifts in the balance of exam questions over the 2014-2024 period. Where the exams in 2014 and 2015 tended toward a blend of simpler Remember and Understand questions with more complex Create-type questions, in subsequent years there was a noticeable shift toward questions of intermediate complexity with a simultaneous reduction in the simpler recall questions. Interestingly, despite the changes in the distributions of the various question types, the 2024 exam was found to contain comparable higher-order content compared to the 2014 exam. In this way, both qualitative and quantitative inductive analysis offers a comprehensive perspective on assessment adaptations that can be used for reflective review of assessment practices.

We have previously demonstrated that a non-natural tetrazole containing peptide (2), which mimics the MEEVD Short Linear Motif (SLiM) found at the Heat Shock Protein 90 (HSP90) C-terminus, disrupts the transient protein-protein interaction (PPI) formed between HSP90 and the HSP70-HSP90 organizing protein (Hop) co-chaperone. However, the native MEEVD SLiM (1) showed negligible inhibitory activity despite similar binding affinity to the interacting HopTPR2A domain. To investigate the origin of this discrepancy, we combined native mass spectrometry (nMS) coupled to ion mobility (IM) with saturation transfer difference (STD) and water ligand observed via gradient spectroscopy (WLOGSY) NMR to interrogate the interaction of peptides 1 and 2 alongside a series of peptide derivatives with HopTPR2A. Collectively, these data revealed that the variation in sequence between peptides 1 and 2 imparts subtle variations in conformational stability and magnetization transfer, indicating that differences in PPI modulation arise from altered binding mode rather than binding affinity. These results not only provide a structural framework for developing peptidomimetic HSP90-Hop PPI inhibitors, but a generalized strategy for exploiting transient PPIs for drug discovery.

South Africa's rich natural resources remain a key driver of its chemical industrialisation but are tainted and constrained by its complex colonial history. Thirty years since the advent of democracy in South Africa, deep sociopolitical inequalities are amplified by an intolerable infectious disease burden amongst disadvantaged communities. In that respect, South Africa shares challenges with many other nations in the Global South; there are limited opportunities for the economic development and growth needed to uplift all strata of society. This Viewpoint examines the role of the chemical sciences in South Africa's unique history and the current state of its academic and industrial sectors, with a focus on the intersection of chemistry, healthcare and biomedical research. We argue that the opportunities offered through chemistry research and development, including local manufacturing, should be exploited and that scientific advancements should be tailored to and integrated with the socioeconomic realities of South Africa for an effective and multidisciplinary approach to improving healthcare outcomes. This Viewpoint aims to inspire a renewed focus on the pivotal role of chemical scientists and their broader societal contributions to combating the country's infectious disease burden and shaping a healthier future for South Africa.

Natural genetic variations profoundly impact drug target interactions causing variations in in vitro biological data. The overall occurrence or "rare genetic variation" is common and enriched within population groups. Incorporating population-level genetic information earlier into the drug discovery pipeline would allow medicinal chemists to contribute to the precision medicine movement, designing drugs with more population relevance.

Herein, the antimycobacterial screening of a series of rifamycin analogues, modified at their C-3 extension, is reported. Overall, these compounds display potent activity against a wild-type Mtb strain assayed in three different growth media. Several promising C-3 extensions are identified through this screen, with compounds featuring rigid tertiary alicyclic hydrazones displaying superior activity to amino compounds. In addition, a general correlative trend between logP and biological activity is observed. This study adds to the growing literature surrounding structure activity relationship pertaining the important C-3 extension of rifamycin, which in addition to a poorly understood role in target engagement, has utility for modulating physicochemical properties, a key condition in antimycobacterial drug discovery.

Kaposi sarcoma associated herpesvirus (KSHV) is a DNA virus that causes Kaposi sarcoma, a cancer of endothelial origin. KSHV uses the activity of host molecular chaperones like Hsp70 and Hsp90 for the folding of host and viral proteins required for productive infection. Hsp70 and Hsp90 chaperones form proteostasis networks with several regulatory proteins known as co-chaperones. Of these, Hsp90-Hsp70 organising protein (HOP) is an early-stage co-chaperone that regulates transfer of folding substrate proteins between the Hsp70 and Hsp90 chaperone systems. While roles for Hsp90 and Hsp70 in KSHV biology have been described, HOP has not previously been studied in this context despite its prominent interaction with both chaperones. Here we demonstrate a novel function for HOP as a new host factor required for effective lytic replication of KSHV in primary effusion cell lines. Data summary The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files. ### Competing Interest Statement The authors have declared no competing interest.

Native mass spectrometric analysis of TPR2A and GrpE with unpurified peptides derived from limited proteolysis of their respective PPI partners (HSP90 C-terminus and DnaK) facilitated efficient, qualitative identification of interfacial epitopes involved in transient PPI formation. Application of this approach can assist in elucidating interfaces of currently uncharacterised transient PPIs.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a DNA virus that causes Kaposi's sarcoma, a cancer of endothelial origin. KSHV uses the activity of host molecular chaperones like Hsp70 and Hsp90 for the folding of host and viral proteins required for productive infection. Hsp70 and Hsp90 chaperones form proteostasis networks with several regulatory proteins known as co-chaperones. Of these, Hsp90-Hsp70-organizing protein (HOP) is an early-stage co-chaperone that regulates the transfer of folding substrate proteins between the Hsp70 and Hsp90 chaperone systems. While the roles for Hsp90 and Hsp70 in KSHV biology have been described, HOP has not previously been studied in this context despite its prominent interaction with both chaperones. Here, we demonstrate a novel function for HOP as a new host factor required for effective lytic replication of KSHV in primary effusion cell lines.

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent for primary effusion lymphoma (PEL), multicentric Castleman’s disease (MCD) and Kaposi’s sarcoma (KS). KSHV is one of the oncoviruses that contribute to 1.5 million new infection-related cancer cases annually. Currently, there are no targeted therapies for KSHV-associated diseases. Through the development of a medium-throughput phenotype-based ELISA screening platform based on KSHV ORF57 protein detection, we screened the Medicines for Malaria Venture (MMV) Pandemic Response Box for non-cytotoxic inhibitors of KSHV lytic replication. MMV1645152 was identified as a promising inhibitor of KSHV lytic replication, suppressing KSHV immediate-early and late lytic gene expression and blocking the production of infectious KSHV virion particles at non-cytotoxic concentrations in cell line models of KSHV infection with or without EBV coinfection. MMV1645152 is a promising hit compound for the development of future therapeutic agents against KSHV-associated malignancies.

Interactions between Short Linear Motifs (SLiMs) and a partner domain are commonly exploited as simplified functional models of transient Protein-Protein Interactions (PPI) for characterizing interfacial associations between partner proteins. In this study, we report the use of a ligand-observed NMR approach, where through unambiguous assignment of 1H resonances of two closely related SLiMs, whilst bound to their partner domain (HopTPR2A ), we could assign STD and WLOGSY NMR signals to specific regions in the peptide backbone. These data revealed subtle alterations in magnetization transfer, resulting from changes in the binding mode of each SLiM respectively. The ability to detect and compare these changes at sub-residue resolution, provided differing fingerprints of SLiM binding. This approach therefore represents a broadly accessible method for identifying binding hot spots and interrogating the impact of structural variations on SLiM-domain interaction stability, and by extension transient PPIs.

The dynamic associations of transient protein–protein interactions (PPIs) are critical mediators of myriad biochemical processes. These specific, low-affinity interactions are often mediated by conserved amino acid sequences or short linear motifs (SLiMs) that interact with corresponding binding domains. The short-lived and dynamic nature of these interactions make their biophysical characterization a significant challenge. This review focuses on the development and future directions of mass spectrometry (MS)-based techniques for elucidating and characterizing SLiM-mediated PPIs. This includes the application of protein footprinting techniques to infer the location of SLiM binding sites and the growing role of native MS for direct observation of protein–SLiM interactions, highlighting their potential for the assessment of small molecule modulation of transient PPIs and the identification of interfacial SLiMs.

The central role of the chaperome in maintaining cellular proteostasis has seen numerous viral families evolve to parasitically exploit host chaperones in their life cycle. The HSP90 chaperone protein and its cochaperone Hop have both individually been shown to be essential factors for Kaposi sarcoma-associated herpesvirus (KSHV) lytic replication. Given the fundamental regulatory role that protein-protein interactions (PPIs) play in cellular biology, we reasoned that disrupting the Hop-HSP90 PPI may provide a new host-based target for inhibiting KSHV lytic replication. This study expands upon a previous report of non-natural peptides, which were found to disrupt the association between the HopTPR2A domain and its interacting HSP90CTD. Here, in addition to providing insight into the structure-activity relationships of PPI inhibition, we show disruption of the full-length Hop-HSP90 PPI. The inhibitory peptides selectively engaged the HopTPR2A domain in cell lysates and when tethered to a cell-penetrating peptide acted as noncytotoxic inhibitors of KSHV lytic replication by lowering the viral load, preventing the production of infectious virions, and reducing the expression of KSHV lytic genes. In addition to tentative evidence of Hop-HSP90 PPI as a much-needed target for KSHV drug discovery, this study represents an important step in understanding viral interactions with the host proteostasis machinery.

Despite Hsp90's well documented promise as a target for developing cancer chemotherapeutics, its inhibitors have struggled to progress through clinical trials. This is, in part, attributed to the cytoprotective compensatory heat shock response (HSR) stimulated through intracellular Hsp90 inhibition. Beyond its intracellular role, secreted extracellular Hsp90 (eHsp90) interacts with numerous pro-oncogenic extracellular clients. This includes fibronectin, which in the tumour microenvironment enhances cell invasiveness and metastasis. Through the rational modification of known Hsp90 inhibitors (SNX2112 and SNX25a) we developed four Hsp90 inhibitory compounds, whose alterations restricted their interaction with intracellular Hsp90 and did not stimulate the HSR. Two of the modified cohort (compounds 10 and 11) were able to disrupt the assembly of the extracellular fibronectin network at non-cytotoxic concentrations, and thus represent promising new tool compounds for studying the druggability of eHsp90 as a target for inhibition of tumour invasiveness and metastasis.

Ethnopharmacological relevance: The use of medicinal plants for central nervous system (CNS)-related ailments, such as epilepsy and anxiety, is prevalent in South Africa. Plants from the Lamiaceae family are commonly used for their therapeutic benefits. Leonotis leonurus (L.) R.Br. has been reported in ethnobotanical literature to have anticonvulsant and anxiolytic effects through the inhalation of pyrolysis products obtained by combustion of the aerial parts. Aim and objectives: To explore the chemical profiles and CNS activity of the smoke extract and isolated constituents of L. leonurus in zebrafish larvae, through anticonvulsive and anxiolytic activity assays. Materials and methods: The smoke extract of L. leonurus was obtained through the combustion of the aerial parts of the plant using a custom-built smoke recovery apparatus. The chemical profile of the smoke constituents was determined using Ultra-Performance Liquid Chromatography coupled with Mass Spectrometry (UPLC-MS). Targeted compounds were subjected to preparative High-Performance Liquid Chromatography for separation before structure elucidation using Nuclear Magnetic Resonance (NMR). The maximum tolerated concentrations, as well as the anxiolytic activity of the smoke extract were determined in five days post fertilisation zebrafish larvae. Reverse-thigmotaxis and locomotor activity of larvae in the light/dark transition assay were used to determine anxiolytic activity. Zebrafish larvae at six days post fertilisation (dpf) were subjected to several concentrations of the smoke constituents of L. leonurus. The baseline locomotor activity of the larvae was tracked for 30 min, prior to addition of pentylenetetrazole (PTZ) to induce seizure-like behaviour in the larvae, after which the locomotor activity of the larvae was once again tracked for an additional 30 min. Results: The UPLC-MS profiles of the smoke extract revealed the presence of two main compounds, leoleorin A and leoleorin B, which were targeted and isolated. Upon subjection to NMR spectroscopy for structure elucidation, the compounds were confirmed to be labdane diterpenoids. Both leoleorin A and leoleorin B, and the smoke extract displayed suppression of the PTZ induced seizure-like behaviour in zebrafish larvae. Under light and dark conditions, the smoke extract and compounds displayed potential anxiolytic activity at different concentrations. Conclusion: Our results suggest that the smoke constituents of L. leonurus may exert anticonvulsant and anxiolytic effects which align with the traditional indications and the mode of administration.

The low number of clinical trials in Africa and biomedical datasets that disproportionately represent populations of European ancestry contribute to the suboptimal efficacy and safety of some medicines in African populations. To address these disparities, we propose greater incorporation of African data into drug discovery and development, as well as the development of African-centric preclinical and clinical models and tools.

The solid-phase synthesis of Met-containing peptides using a fluorenylmethoxycarbonyl (Fmoc)/tert-butyl (tBu) protection scheme is inevitably accompanied by two stubborn side reactions, namely, oxidation and S-alkylation (tert-butylation), which result in the formation of Met(O) and sulfonium salt impurities of the target peptide, respectively. These two reactions are acid-catalyzed, and they occur during the final trifluoroacetic (TFA)-based acidolytic cleavage step. Herein, we developed two new cleavage solutions that eradicate the oxidation and reduce S-alkylation. TFA-anisole-trimethylsilyl chloride (TMSCl)-Me2S-triisopropylsilane (TIS) containing 1 mg of triphenyl phosphine per mL of solution was the optimal mixture for Cys-containing peptides, while for the remaining peptides, TIS was not required. Both cleavage solutions proved to be excellent when sensitive amino acids such as Cys and Trp were involved. TMSCl did not affect either of these sensitive amino acids. Reversing the sulfonium salt to free Met-containing peptide was achieved by heating the peptide at 40 °C for 24 h using 5% acetic acid.

Clinton Veale and Fanie van Heerden discuss the story of natamycin. From its humble telluric origins in Pietermaritzburg, this unique antimicrobial agent has risen to become a mainstay of the food and beverages industry.

The young, fast‐growing population of Africa means that harnessing the economic benefits of scientific research is critical to sustained and equitable growth in the continent. Moreover, the whole world would benefit from the added intellectual contribution that would come from nurturing African science. The high burden of neglected diseases in Africa makes chemical biology a particularly important field. In this editorial, the reconvergence of science conducted at the interface of chemistry and biology is placed in the context of African participation, its importance to global science and the unique blend of supporting and hindering factors that influence African scientific contributions. The new Biological and Medicinal Chemistry in Africa special collection showcases a broad spectrum of African chemical biology.