<p>The synthesis of novel oxadiazole antibiotics more water soluble than previously published analogues within the group will be discussed in this thesis as part of synthesizing a library with increased sp3 character.  These analogues were tested against S. aureus and MRSA strains to determine the most active compounds then percent hemolysis confirmed little RBC lysis among the compounds.  Synergistic activity was also tested for HSGN-2241 previously synthesized within the group.  Biofilm eradication assays were completed for HSD 1919 alongside time kill assays.</p>

A interação de várias substancias bioativas com monocamadas de fosfolipídios foi investigada usando isotermas de pressão e potencial de superfície, incluindo as drogas farmacológicas dipiridamol (DIP), clopromazina (CPZ) e trifluoperazina (TFP), além da melatonina (MEL) e o colesterol (COL). Os fosfolipídios empregados foram o zwiteriônico dipalmitoil fosfatidil colina (DPPC) e o aniônico dipalmitoil fosfatidil glicerol (DPPG) espalhados na superfície de água ultrapura, sendo que as monocamadas servem como modelo simples de membranas. A cooperatividade na interação entre fosfolipídios e moléculas com atividade biológica foi essencial para entender os acentuados efeitos na expansão (ou condensação) das monocamadas e as mudanças no momento de dipolo (até 10% de aumento na expansão em relação à monocamada do fosfolipídio puro para as misturas DIP/DPPC) que ocorreram a concentrações molares muito baixas entre 0,2-0,4% do DIP. Tais efeitos foram observados para todas as cinco substâncias investigadas, em todos os regimes de pressão. Nas altas concentrações, o comportamento da interação depende do tipo de mólecula e também de se a monocamada é de DPPC ou DPPG. Para o DPPC, as drogas farmacológicas foram expelidas da interface em vários graus a altas pressões, e existia um máximo de concentração da droga acima do qual ocorria a saturação, provavelmente porque as moléculas em excesso foram para a subfase. Essas concentrações críticas foram de 2% em mol para o DIP e a CPZ e de 5% em mol para a TFP. Para o DIP, em particular, os resultados das isotermas foram correlacionados com experimentos de espectroscopia de FTIR e microscopia de fluorescência \"in situ\", realizados por colaboradores, os quais permitiram a determinação de uma localização precisa da droga estudada. Não existe inserção do DIP na região da cauda hidrofóbica da monocamada do DPPC, com a interação ocorrendo com o grupo fosfato no zwiteríon, cujas pequenas mudanças na orientação induzidas pelo DIP levam a grandes mudanças no momento de dipolo. Como o DPPG está carregado negativamente sobre a superfície da água pura, não existe saturação nos efeitos de expansão com o aumento da concentração das drogas. O aumento do momento de dipolo efetivo na monocamada mista é atribuído a alterações na densidade de carga superficial pela adsorção da droga catiônica, que reduz a contribuição negativa do potencial da dupla camada, quando comparado com o da monocamada de DPPG puro. Os resultados do COL e a MEL devem ser considerados separadamente devido a sua natureza distinta, embora um comportamento cooperativo também tenha observado com grandes efeitos nas baixas concentrações. Tanto o COL como o MEL induzem mudanças na expansão das monocamadas de DPPC até a máxima concentração empregada, 20% molar. Para o COL foi observado um efeito de condensação a baixas concentrações, o qual foi seguido por uma expansão a altas concentrações, confirmando assim resultados prévios da literatura. Todas as monocamadas mistas COL/DPPG apresentavam-se expandidas, também confirmando alguns resultados da literatura para lipídios (diferentes do DPPC) quando misturados com o COL. A interação da MEL com o DPPC foi essencialmente similar à do COL, apesar do fato de a MEL pura não formar monocamadas estáveis. Sua interação com o DPPG foi peculiar já que o efeito que esta induz satura a 5% em mol. Isto também difere do comportamento das drogas farmacológicas. A MEL é neutra em todos os pHs, portanto, sua intenção com as membranas modelo de DPPG e DPPC só pode ocorrer via dipolo. O mesmo se aplica ao colesterol, o que justifica as diferenças no comportameto destas duas moléculas quando comparadas com as drogas (DIP, CPZ, TFP), que são carregadas sobre a água pura, nas misturas com os dois fosfolipídios (DPPG e DPPC). / The interaction of various bioactive substances with phospholipids monolayers has been investigated using surface pressure and surface potential isotherms, which include the pharmaceutical drugs dipyridamole (DIP), chlorpromazine (CPZ) and trifluoperazine (TFP), in addition to melatonin (MEL) and cholesterol (COL). The phospholipids employed were the zwitterionic dipalmitoyl phosphatidyl choline (DPPC) and the anionic dipalmitoyl phosphatidyl glycerol (DPPG) spread onto ultra pure water surfaces, where the monolayers served as simple model membrane systems. Cooperativity in the interaction between phospholipid and bioactive molecules was essential to account for the large effects of expansion (up to 10% increase in area in relation to the pure phospholipid monolayer for the DIP/DPPC mixture) of the monolayers and changes in dipole moment, which occurred at very low concentrations, e.g. 0.2 - 0.4 mol% of the substance. Such large effects were observed for all 5 substances investigated, at all surface pressure regimes. At higher concentrations, the interaction behavior depended on the type of molecule and also on whether the host monolayer was DPPC or DPPG. For DPPC, the pharmaceutical drugs were expelled at varying degrees from the interface at high surface pressures, and there was a maximum drug concentration above which the effects saturated, probably because the molecules in excess were lost to the subphase. These critical concentrations were 2mol% for DIP and CPZ and 5mol% for TFP. For DIP, in particular, the results from isotherm were correlated with in situ FTIR spectroscopy and fluorescent microscopy experiments, carried out by collaborators, which allowed the precise location of the drug to be determined. There is no insertion of DIP into the hydrophobic tail region of the DPPC monolayer, with interaction taking place with the phosphate group in the zwitterion, whose small changes in orientation induced by DIP lead to the large changes in dipole moment. Because DPPG is negatively charged on a pure water surface monolayer, there is no saturation of the expansion effects with the increase in drug concentration. The increase in the effective dipole moment of the mixed monolayers are attributed to alterations in the surface charge density by adsorption of the cationic drugs, which then reduces the negative contribution of the double-layer potential as compared to the pure DPPG monolayer. The results for COL and MEL must be considered separately owing to their distinct nature, even though a cooperative behavior was also observed with large effects at low concentrations. Both COL and MEL induce changes in the DPPC monolayers up to the highest concentration employed, viz. 20mol%. For COL, a condensation effect was observed at low concentrations, which was followed by monolayer expansion at high concentrations, thus confirming previous results in the literature. All COL/DPPG monolayers were more expanded than pure DPPG, also confirming previous results from the literature. While the interaction of MEL with DPPC was essentially similar to that of COL, in spite of the fact that MEL does not form stable monolayers on its own, its interaction with DPPG was somewhat peculiar in that the effects it induced saturate at 5mol%. This also differs from the behavior of the pharmaceutical drugs. MEL is neutral over a wide range of pHs, and therefore its interaction with DPPC and DPPG monolayers must occur via dipole interaction. The same applies to COL, and this explains why the behavior of these two substances is different from the drugs (DIP, CPZ and TFP) that are charged on the water surface, in the interaction with DPPC and DPPG.

A interação de várias substancias bioativas com monocamadas de fosfolipídios foi investigada usando isotermas de pressão e potencial de superfície, incluindo as drogas farmacológicas dipiridamol (DIP), clopromazina (CPZ) e trifluoperazina (TFP), além da melatonina (MEL) e o colesterol (COL). Os fosfolipídios empregados foram o zwiteriônico dipalmitoil fosfatidil colina (DPPC) e o aniônico dipalmitoil fosfatidil glicerol (DPPG) espalhados na superfície de água ultrapura, sendo que as monocamadas servem como modelo simples de membranas. A cooperatividade na interação entre fosfolipídios e moléculas com atividade biológica foi essencial para entender os acentuados efeitos na expansão (ou condensação) das monocamadas e as mudanças no momento de dipolo (até 10% de aumento na expansão em relação à monocamada do fosfolipídio puro para as misturas DIP/DPPC) que ocorreram a concentrações molares muito baixas entre 0,2-0,4% do DIP. Tais efeitos foram observados para todas as cinco substâncias investigadas, em todos os regimes de pressão. Nas altas concentrações, o comportamento da interação depende do tipo de mólecula e também de se a monocamada é de DPPC ou DPPG. Para o DPPC, as drogas farmacológicas foram expelidas da interface em vários graus a altas pressões, e existia um máximo de concentração da droga acima do qual ocorria a saturação, provavelmente porque as moléculas em excesso foram para a subfase. Essas concentrações críticas foram de 2% em mol para o DIP e a CPZ e de 5% em mol para a TFP. Para o DIP, em particular, os resultados das isotermas foram correlacionados com experimentos de espectroscopia de FTIR e microscopia de fluorescência \"in situ\", realizados por colaboradores, os quais permitiram a determinação de uma localização precisa da droga estudada. Não existe inserção do DIP na região da cauda hidrofóbica da monocamada do DPPC, com a interação ocorrendo com o grupo fosfato no zwiteríon, cujas pequenas mudanças na orientação induzidas pelo DIP levam a grandes mudanças no momento de dipolo. Como o DPPG está carregado negativamente sobre a superfície da água pura, não existe saturação nos efeitos de expansão com o aumento da concentração das drogas. O aumento do momento de dipolo efetivo na monocamada mista é atribuído a alterações na densidade de carga superficial pela adsorção da droga catiônica, que reduz a contribuição negativa do potencial da dupla camada, quando comparado com o da monocamada de DPPG puro. Os resultados do COL e a MEL devem ser considerados separadamente devido a sua natureza distinta, embora um comportamento cooperativo também tenha observado com grandes efeitos nas baixas concentrações. Tanto o COL como o MEL induzem mudanças na expansão das monocamadas de DPPC até a máxima concentração empregada, 20% molar. Para o COL foi observado um efeito de condensação a baixas concentrações, o qual foi seguido por uma expansão a altas concentrações, confirmando assim resultados prévios da literatura. Todas as monocamadas mistas COL/DPPG apresentavam-se expandidas, também confirmando alguns resultados da literatura para lipídios (diferentes do DPPC) quando misturados com o COL. A interação da MEL com o DPPC foi essencialmente similar à do COL, apesar do fato de a MEL pura não formar monocamadas estáveis. Sua interação com o DPPG foi peculiar já que o efeito que esta induz satura a 5% em mol. Isto também difere do comportamento das drogas farmacológicas. A MEL é neutra em todos os pHs, portanto, sua intenção com as membranas modelo de DPPG e DPPC só pode ocorrer via dipolo. O mesmo se aplica ao colesterol, o que justifica as diferenças no comportameto destas duas moléculas quando comparadas com as drogas (DIP, CPZ, TFP), que são carregadas sobre a água pura, nas misturas com os dois fosfolipídios (DPPG e DPPC). / The interaction of various bioactive substances with phospholipids monolayers has been investigated using surface pressure and surface potential isotherms, which include the pharmaceutical drugs dipyridamole (DIP), chlorpromazine (CPZ) and trifluoperazine (TFP), in addition to melatonin (MEL) and cholesterol (COL). The phospholipids employed were the zwitterionic dipalmitoyl phosphatidyl choline (DPPC) and the anionic dipalmitoyl phosphatidyl glycerol (DPPG) spread onto ultra pure water surfaces, where the monolayers served as simple model membrane systems. Cooperativity in the interaction between phospholipid and bioactive molecules was essential to account for the large effects of expansion (up to 10% increase in area in relation to the pure phospholipid monolayer for the DIP/DPPC mixture) of the monolayers and changes in dipole moment, which occurred at very low concentrations, e.g. 0.2 - 0.4 mol% of the substance. Such large effects were observed for all 5 substances investigated, at all surface pressure regimes. At higher concentrations, the interaction behavior depended on the type of molecule and also on whether the host monolayer was DPPC or DPPG. For DPPC, the pharmaceutical drugs were expelled at varying degrees from the interface at high surface pressures, and there was a maximum drug concentration above which the effects saturated, probably because the molecules in excess were lost to the subphase. These critical concentrations were 2mol% for DIP and CPZ and 5mol% for TFP. For DIP, in particular, the results from isotherm were correlated with in situ FTIR spectroscopy and fluorescent microscopy experiments, carried out by collaborators, which allowed the precise location of the drug to be determined. There is no insertion of DIP into the hydrophobic tail region of the DPPC monolayer, with interaction taking place with the phosphate group in the zwitterion, whose small changes in orientation induced by DIP lead to the large changes in dipole moment. Because DPPG is negatively charged on a pure water surface monolayer, there is no saturation of the expansion effects with the increase in drug concentration. The increase in the effective dipole moment of the mixed monolayers are attributed to alterations in the surface charge density by adsorption of the cationic drugs, which then reduces the negative contribution of the double-layer potential as compared to the pure DPPG monolayer. The results for COL and MEL must be considered separately owing to their distinct nature, even though a cooperative behavior was also observed with large effects at low concentrations. Both COL and MEL induce changes in the DPPC monolayers up to the highest concentration employed, viz. 20mol%. For COL, a condensation effect was observed at low concentrations, which was followed by monolayer expansion at high concentrations, thus confirming previous results in the literature. All COL/DPPG monolayers were more expanded than pure DPPG, also confirming previous results from the literature. While the interaction of MEL with DPPC was essentially similar to that of COL, in spite of the fact that MEL does not form stable monolayers on its own, its interaction with DPPG was somewhat peculiar in that the effects it induced saturate at 5mol%. This also differs from the behavior of the pharmaceutical drugs. MEL is neutral over a wide range of pHs, and therefore its interaction with DPPC and DPPG monolayers must occur via dipole interaction. The same applies to COL, and this explains why the behavior of these two substances is different from the drugs (DIP, CPZ and TFP) that are charged on the water surface, in the interaction with DPPC and DPPG.

<p dir="ltr">This study has focused on the role of novel boronic acid (BA) and nicotinamide-ponatinib analogs to address current limitations in the treatment of difficult-to-treat cancers including renal, breast and lung cancer. As is well-known, CLK and ROCK have been implicated as oncogenic kinases across several cancer types. However, there are research gaps in the development of CLK/ROCKi. For instance, currently none of the CLKi have been FDA-approved. This study has identified novel BA-containing pyrazolo[4,3-<i>f</i>]quinoline scaffolds that are potent, dual CLK/ROCKi, which are highly active against the renal cancer cell line, Caki-1 based on the NCI screening data. Based on kinase and cancer cell line screening, the top compounds were identified and mechanistic studies indicated that the compounds promoted DNA damage in Caki-1. We also gained insight into the binding modes of the compounds via docking analysis. Furthermore, flow cytometry analysis indicated that the top compounds promote cell cycle arrest. Additionally, qPCR and western analysis indicated that the top compound, <b>HSD1791</b>, suppresses cyclinD/Rb pathway, thereby providing a mechanistic basis for cell cycle arrest. Concerning the challenges in the treatment of breast and lung cancer, it is known that despite advances in chemotherapy and immunotherapy, the survival rate of patients is poor at the advanced stage of the diseases. Oncogenic kinases such as p70S6K and MNK have been independently implicated in breast and lung tumorigenesis, however synergistically targeting MNK/p70S6K pathways using single agents remains a challenge. In this study, we have identified the novel lead candidate, <b>HSND80</b>, which is a potent dual MNK/p70S6Ki with remarkable activity against breast and non-small cell lung cancer cell lines. We identified the mechanism of tumor cell growth suppression using proteomics, immunoblotting, and cell cycle analysis. Moreover, <b>HSND80</b> has demonstrated tumor growth suppression effects <i>in vivo</i>. Additionally, pharmacokinetics, plasma protein binding, and hERG safety analysis indicated <b>HSND80</b> has suitable drug-like properties. Together, these findings indicate that it has promising functions as an anticancer therapeutic. In conclusion, this study has focused on identifying and characterizing novel pyrazolo[4,3-<i>f</i>]quinoline scaffolds and nicotinamide ponatinib analogs as promising tumor-agnostic therapeutics.</p>

<p>Cyclobutane pyrimidine dimers (CPD) are the predominant DNA lesions formed upon exposure of this biopolymer to sunlight. Given the potentially dire biological consequences of DNA lesions, there is a need to fully characterize their behaviour, with an eye towards understanding their complete reactivity and as a possible means to detect and quantify their presence in the genome. The work described in this dissertation describes studies of the alkaline reactivity of CPD lesions generated within dinucleotide & polynucleotide strands. It was found that CPD-TpT is generally inert under alkaline conditions at room temperature, which is in agreement with earlier studies on alkaline hydrolysis of CPD-thymine and CPD-thymidine. However, a re-evaluation of the same reaction in the presence of ¹⁸O labelled water demonstrated that, similar to other UV-induced DNA lesions containing a saturated pyrimidine ring, CPD undergoes a water addition at the C4=O group of the nucleobase leading to the formation of a hemiaminal intermediate. This intermediate, however, does not lead to hydrolysis products and completely reverts to starting material under those same conditions. Moreover, the two C4=O groups present on 3′ and 5′-thymines in a CPD molecule show different chemical reactivities, with the 3′ C4=O group having greater affinity towards water addition as compared to the one on 5′ end, a fact reflected in different rates of exchange with the incoming nucleophile leading to the hemiaminal intermediate. The ¹⁸O labelling reaction was also investigated in CPD lesions generated within oligonucleotides to probe the cause of asymmetry between the 3′ <i>vs</i> 5′ C4=O groups; ultimately, it was determined that the asymmetric reactivity observed to occur between the two C4=O groups was an intrinsic property of the CPD molecule and did not arise as a result of asymmetry in a dinucleotide setting.</p><p><br></p> <p>In addition to the above studies, during the course of the investigation of the nucleophilic reactivity of CPD, a chemical reaction was observed leading to what appeared to be the rapid and total chemical reversal of CPD lesions to the original TpT (thymine-thymine dinucleotide)! This “repair” reaction occurred when CPD reacted with hydrazine, and appears facilitated by an inert atmosphere under which it rapidly proceeds to completion at room temperature.</p><br>

<p> The study of proteasome is a rapidly evolving field with multifaceted implications in neuroscience, aging, and cancer. Recent developments structural biology of the proteasome machinery has catapulted the drug discovery and targeted protein degradation. The success of proteasome inhibitors like Bortezomib and Ixazomib has also led to new interests in developing more precise inhibitors for the various proteasome isoforms. Proteasome activation is a relatively new field, and much has to be done in the field. The 20S CP is an emerging target in chemical biology and drug discovery for its implications in maintaining protein homeostasis and immune regulation. The central theme of the thesis is to study the proteasome in cellular contexts to develop new chemical biology tools to study the proteasome and its modulation by small molecules and probes in cellular contexts to ameliorate protein accumulation-mediated neurodegeneration </p>

<p dir="ltr">Sterile manufacturing is multifaceted. Each aspect seeks to improve the process of producing drug products absent of impurities. Bacteriophages can benefit greatly from sterile manufacturing which would amplify their already vast range of applications. Novel bacteriophage discovery and annotation, implemented within a classroom setting, can aid in building the foundation of bacteriophages for use in clinical applications. High-Performance Liquid Chromatography (HPLC) can detect impurities and test compatibilities in the final product. Oxytocin and its interaction with tranexamic acid (TXA) provide an excellent example of how HPLC use can be critical in sterile manufacturing as well as build a baseline for which bacteriophages may be utilized in sterile production. A quality scorecard for drug products provides an additional metric that can be used by governing agencies and consumers to analyze drug products of similar bioequivalence and subsequently grade them. The development of a scorecard will provide a guideline to improve the sterile manufacturing of drug products and biologics such as bacteriophages. A literary analysis of lipid nanoparticles presents a future application for synthetically manufactured bacteriophages. The conclusions gathered from this work can be utilized as a case study for working professionals who aim to implement advancements in sterile manufacturing within their industry.</p>

<p dir="ltr">UBE2C is upregulated in castration-resistant prostate cancer and shows strong correlation with high tumor grade. Currently, the scarcity of UBE2C inhibitors is alarming. This study is the first to report UBE2C post-translational modulation mediated by LIMK2 kinase. A proteome-wide screen previously conducted in the Shah lab has identified UBE2C as a direct substrate of LIMK2 using an innovative chemical genetic approach. LIMK2 regulates UBE2C in a variety of ways. First, LIMK2 directly associates with UBE2C in cells. Second, LIMK2 phosphorylates UBE2C at S123 and increases its stability at the protein level. Third, LIMK2 upregulates UBE2C mRNA and protein expression levels in cells. Contrary to its well-established function as an enzyme involved in the ubiquitin-proteosome pathway, UBE2C stabilizes LIMK2 protein expression in a reciprocal loop. This study is the first to show UBE2C stabilizing its substrate. Likewise, UBE2C increases LIMK2 mRNA and protein levels; however, the mechanism is to be elucidated. LIMK2-UBE2C loop is extremely oncogenic creating CRPC pathogenesis <i>in vivo</i>. Targeting LIMK2 is a suitable approach to effectively degrade both UBE2C and LIMK2 which leads to significant inhibition of tumor formation, cancer stem cell phenotype and epithelial to mesenchymal transition <i>in vivo</i>. Additionally, CDK1 for the longest time was thought to be the only protein of the cyclin dependent kinase family which binds to and is activated by cyclin B1 to regulate cell cycle progression. We first showed CDK5 activity in cell division and its importance in maintaining mitotic fidelity. We first established the activation of CDK5 by cyclin B1 <i>in vitro</i>. The phospho-mimetic CDK5 was observed to be less active when bound to cyclin B1 than its wild-type counterpart.</p>

<p dir="ltr">Cancer is the second leading cause of death worldwide, and there is a continued need for effective treatments to combat the disease. A key challenge in cancer therapy persists in the form of therapeutic resistance. While kinase inhibitors (KIs) have shown promise in treating cancer patients with dysregulated protein kinases, treatment failures are common, highlighting the urgent need to address this issue. Despite the approval of 80 protein kinase inhibitors by the United States Food and Drug Administration (FDA), and numerous others in clinical trials, the chemical space explored for protein kinase inhibitors remains limited. Most FDA-approved kinase inhibitors share common core moieties, such as indazole, quinoline, pyrazole, and pyrimidine, indicating a lack of diversification in drug development in this area.</p><p dir="ltr">Efforts to expand the chemical space have led to the identification of a novel 3<i>H</i>-pyrazolo-[4,3-<i>f</i>]quinoline core by the Sintim group. This scaffold can be efficiently synthesized through the Doebner–Povarov multicomponent reaction using readily available ketones, heteroaromatic aldehydes, and 5-aminoindazole. This multicomponent chemistry affords small molecules which inhibit disease-associated protein kinases with sub-nanomolar IC₅₀ values. Additionally, the scaffold presents a unique opportunity to tune for selectivity via judicious substitution patterns, allowing us to target numerous disease-driving kinases, such as FLT3, haspin, and CLK, with the use of simple multi-component chemistry.</p><p dir="ltr">From this work emerged lead amide-containing compound HSK205, which potently inhibits FLT3 and haspin and shows impressive potencies against FLT3-driven acute myeloid leukemia cell lines, with GI₅₀ values between 2 and 20 nM. Western blot analyses indicate that HSK205 inhibits the phosphorylation of FLT3 and histone H3 (substrate of haspin) in Molm-14 AML cells. Further exploration led to the discovery of lead CLK inhibitors, such as HSK1132 and HSK3110, which inhibit the growth of multiple myeloma cell lines <i>in vitro</i> with GI₅₀ values as low as 17 nM. Additionally, these compounds are orally bioavailable and reduce the growth of multiple myeloma RPMI-8226 xenograft model in mice by 69%.</p>

<p dir="ltr">Post-translational modifications (PTMs) play a crucial role in regulating protein function and location. Protein AMPylation, the addition of adenosine monophosphate (AMP), significantly influences protein trafficking, stability, and pathogenic virulence. The Fic Domain family of proteins targets hydroxyl-containing amino acid residues (Ser, Thr, or Tyr), catalyzing the addition of various phosphate-containing moieties such as nucleoside monophosphates (NMPs), phosphocholine, and phosphate. Using gene mining techniques, Dr. Seema Mattoo’s group has identified a clade of Fic domain containing proteins typified by the enzyme originating from <i>Bordetella bronchiseptica</i> (BbFic) which prefers utilizing guanosine triphosphate (GTP) as a substrate over other nucleotides. To understand the physiological role of GMPylation, identifying the proteins modified by BbFic is a first critical step and can be accomplished via mass spectrometry-based proteomics. For a low stoichiometry PTM like GMPylation, however, there is a need to develop chemical tools that enable the targeted enrichment of modified protein. Identifying key interactions between substrate proteins and the BbFic nucleotide binding site will enable development of highly specific molecular tags for Fic substrates.</p><p dir="ltr">The goal of this research project, therefore, is to design chemical probes to tag Fic enzyme substrates, thereby facilitating the identification of GMPylated proteins in chemical proteomics workflows. A set of ATP and GTP analogues carrying either alkyne or azide handles were proposed as possible probes. While 8-azido guanosine showed a high docking score in our in-silico study, literature reports highlight its chemical instability upon exposure to air and light. An alternative probe, the 8-ethynyl guanosine, also showed a high docking score and docks in the same position and orientation as guanosine (the natural ligand) but necessitates synthetically challenging via cross-coupling reactions.</p><p dir="ltr">We considered multiple GMP analogues as potential molecular tags with the assistance of molecular docking with the BbFic enzyme. With predicted binding affinities in hand, we prioritized candidate GTP analogs for synthesis to probe the BbFic-mediated protein GMPylation process. While N6 propargyl guanosine serves as a lead probe for AMPylation, computational analysis reveals challenges with O6 due to its altered hydrogen bond donor/acceptor presentation. The distinctive chemical properties of guanosine, compared to adenosine, require a thorough evaluation of protective group strategies, as not all synthetic methodologies used for ATP analogue synthesis are applicable to GTP analogues. Isolating the triphosphate analogue proved challenging, although purification of the monophosphorylated counterpart is feasible. The Protide analogue benefits from phosphate charge masking, which facilitates purification. While much work remains until the physiological role of GMPylation can be determined, important progress has been made in the design and synthesis of chemical tools for studying this newly discovered PTM.</p>