Recent Developments in Flavin-Based Catalysis:Enzymatic Sulfoxidation

The synthesis of optically active sulfoxides, compounds due to their unique properties, has been a main target for synthetic organic chemistry. Recent efforts in the field of biocatalysis have allowed the preparation of enantiopure sulfoxides starting from the corresponding sulfides while using relatively mild conditions. In fact, several different types of redox biocatalysts have been found that can catalyze enantio- and/or regioselective sulfoxidations. The most promising group of enzymes able to perform selective sulfoxidations is the flavin-containing monooxygenases (FMOs). Enzymes containing a flavin cofactor have already been widely studied and used in organic synthesis, especially in reduction and/or oxidation processes. This chapter highlights the recent efforts in the preparation of chiral sulfoxides catalyzed by different types of flavoenzymes, with special attention to the parameters that can improve their catalytic properties. Novel approaches that allow performing selective sulfoxidations in which modified flavin systems are used are also discussed.</p

Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity

Non-covalent interactions are known to play a key role in biological compounds due to their stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings, such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl- 1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and aromatic interactions involving pyrimidine and phenyl rings in both complexes drives their self-assembly. Noncovalent interactions involving aromatic rings are key processes in both chemical and biological recognition, contributing to overall complex stability and forming recognition motifs. It is noteworthy that in Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between pairs of antiparallel triazolopyrimidine rings mimick basepair interactions physiologically occurring in DNA (Fig.1). M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a distorted octahedral structure, with C-Sn-C bond angles lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2 is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure. The compounds were screened for their in vitro antibacterial activity on a group of reference staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative pathogens [4] . We tested the biological activity of all the specimen against a group of staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P. aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also resulted active against methicillin resistant S. epidermidis RP62A

Phototrophic Bacteria

Microorganisms is pleased to publish this book, which reprints papers that appeared in a Special Issue on “Phototrophic Bacteria”, with Guest Editors Robert Blankenship and Matthew Sattley. This Special Issue included research on all types of phototrophic bacteria, including both anoxygenic and oxygenic forms. Research on these bacterial organisms has greatly advanced our understanding of the basic principles that underlie the energy storage that takes place in all types of photosynthetic organisms, including both bacterial and eukaryotic forms. Topics of interest include: microbial physiology, microbial ecology, microbial genetics, evolutionary microbiology, systems microbiology, agricultural microbiology, microbial biotechnology, and environmental microbiology, as all are related to phototrophic bacteria

Creatine Supplementation for Health and Clinical Diseases

Creatine plays a critical role in cellular metabolism, primarily by binding with phosphate to form phosphocreatine (PCr) as well as shuttling high-energy phosphate compounds in and out of the mitochondria for metabolism. Increasing the dietary availability of creatine increases the tissue and cellular availability of PCr, and thereby enhances the ability to maintain high-energy states during intense exercise. For this reason, creatine monohydrate has been extensively studied as an ergogenic aid for exercise, training, and sport. Limitations in the ability to synthesize creatine and transport and/or store dietary creatine can impair metabolism and is a contributor to several disease states. Additionally, creatine provides an important source of energy during metabolically stressed states, particularly when oxygen availability is limited. Thus, researchers have assessed the role of creatine supplementation on health throughout the lifespan, as well as whether creatine availability may improve disease management and/or therapeutic outcomes. This book provides a comprehensive overview of scientific and medical evidence related to creatine's role in metabolism, health throughout the lifespan, and our current understanding of how creatine can promote brain, heart, vascular and immune health; reduce the severity of musculoskeletal and brain injury; and may provide therapeutic benefits in glucose management and diabetes, cancer therapy, inflammatory bowel disease, and post-viral fatigue