Chandrananimycins A-C: Production of novel anticancer antibiotics from a marine Actinomadura sp isolate M048 by variation of medium composition and growth conditions

In our screening of marine actinomycetes for bioactive principles, three novel antibiotics designated as chandrananimycin A (3c), B (3d) and C (4) were isolated from the culture broth of a marine Actinomadura sp. isolate M045. The structures of the new antibiotics were determined by detailed interpretation of mass, 1 D and 2 D NMR spectra.

An ONIOM Study of the Bergman Reaction: A Computationally Efficient and Accurate Method for Modeling the Enediyne Anticancer Antibiotics

The Bergman cyclization of large polycyclic enediyne systems that mimic the cores of the enediyne anticancer antibiotics was studied using the ONIOM hybrid method. Tests on small enediynes show that ONIOM can accurately match experimental data. The effect of the triggering reaction in the natural products is investigated, and we support the argument that it is strain effects that lower the cyclization barrier. The barrier for the triggered molecule is very low, leading to a reasonable half-life at biological temperatures. No evidence is found that would suggest a concerted cyclization/H-atom abstraction mechanism is necessary for DNA cleavage.

Semiempirical Study of the Bergman Reaction: Towards a Computationally Efficient and Accurate Method for Modeling Enediyne Anticancer Antibiotics

Over the past 7 years, the enediyne anticancer antibiotics have been widely studied due to their DNA cleaving ability. The focus of these antibiotics, represented by kedarcidin chromophore, neocarzinostatin chromophore, calicheamicin, esperamicin A, and dynemicin A, is on the enediyne moiety contained within each of these antibiotics. In its inactive form, the moiety is benign to its environment. Upon suitable activation, the system undergoes a Bergman cycloaromatization proceeding through a 1,4-dehydrobenzene diradical intermediate. It is this diradical intermediate that is thought to cleave double-stranded dna through hydrogen atom abstraction. Semiempirical, semiempiricalci, Hartree–Fock ab initio, and mp2 electron correlation methods have been used to investigate the inactive hex-3-ene-1,5-diyne reactant, the 1,4-dehydrobenzene diradical, and a transition state structure of the Bergman reaction. Geometries calculated with different basis sets and by semiempirical methods have been used for single-point calculations using electron correlation methods. These results are compared with the best experimental and theoretical results reported in the literature. Implications of these results for computational studies of the enediyne anticancer antibiotics are discussed.

Statistical Analysis of Data on Linker Histones/DNA Interactions

2000 Mathematics Subject Classification: 62P10, 92C40

An introduction to anticancer drugs

An introduction to anticancer drugs 24.1 Introduction 24.2 The rationale behind anticancer drug therapy 24.3 Drugs used in cancer 24.3.1 Alkylating agents 24.3.2 Cytotoxic antibiotics 24.3.3 Antimetabolites 24.3.4 Microtubule inhibitors 24.3.5 Monoclonal antibodies 24.3.6 Steroid hormones and their antagonists 24.3.7 Other treatments

Glycosylation and Glycodiversification in Polyketide Antibiotics: Unraveling Biosynthetic Steps in Nogalamycin Formation

Soil-dwelling Streptomyces bacteria are known for their ability to produce biologically active compounds such as antimicrobial, immunosuppressant, antifungal and anticancer drugs. S. nogalater is the producer of nogalamycin, a potential anticancer drug exhibiting high cytotoxicity and activity against human topoisomerases I and II. Nogalamycin is an anthracycline polyketide comprising a four-ring aromatic backbone,a neutral deoxy sugar at C7, and an amino sugar attached via an O–C bond at C1 and a C–C bond between C2 and C5´´. This kind of attachment of the amino sugar is unusual thus making the structure of the compound highly interesting. The sugar is also associated with the biological activity of nogalamycin, as it facilitates binding to DNA. Furthermore, the sugar moieties of anthracyclines are often crucial for their biological activity. Together the interesting attachment of the amino sugar and the general reliance of polyketides on the sugar moieties for bioactivity have made the study of the biosynthesis of nogalamycin attractive. The sugar moieties are typically attached by glycosyltransferases, which use two substrates: the donor and the acceptor. The literature review of the thesis is focused on the glycosylation of polyketides and the possibilities to alter their glycosylation patterns. My own thesis work revolves around the biosynthesis of nogalamycin. We have elucidated the individual steps that lead to its rather unique structure. We reconstructed the whole biosynthetic pathway in the heterologous host S. albus using a cosmid and a plasmid. In the process, we were able to isolate new compounds when the cosmid, which contains the majority of the nogalamycin gene cluster, was expressed alone in the heterologous host. The new compounds included true intermediates of the pathway as well as metabolites, which were most likely altered by the endogenous enzymes of the host. The biological activity of the most interesting new products was tested against human topoisomerases I and II, and they were found to exhibit such activities. The heterologous expression system facilitated the generation of mutants with inactivated biosynthetic genes. In that process, we were able to identify the functions of the glycosyltransferases SnogE and SnogD, solve the structure of SnogD, discover a novel C1-hydroxylase system comprising SnoaW and SnoaL2, and establish that the two homologous non-heme α-ketoglutarate and Fe2+ dependent enzymes SnoK and SnoN catalyze atypical reactions on the pathway. We demonstrated that SnoK was responsible for the formation of the additional C–C bond, whereas SnoN is an epimerase. A combination of in vivo and in vitro techniques was utilized to unravel the details of these enzymes. Protein crystallography gave us an important means to understand the mechanisms. Furthermore, the solved structures serve as platforms for future rational design of the enzymes.

Validity and reliability of instruments designed to measure factors influencing the overuse of antibiotics

Background: Antibiotic overuse is a global public health issue that is influenced by several factors. The degree and prevalence of antibiotic overuse is difficult to measure directly. A more practical approach, such as the use of a psycho-social measurement instrument, might allow for the observation and assessment of patterns of antibiotic use. Study objective: The aim of this paper is to review the nature, validity, and reliability of measurement scales designed to measure factors associated with antibiotic misuse/overuse. Design: This study is descriptive and includes a systematic integration of the measurement scales used in the literature to measure factors associated with antibiotic misuse/overuse. The review included 70 international scientific publications from 1992 to 2010. Main results: Studies have presented scales to measure antibiotic misuse. However, the workup of these instruments is often not mentioned, or the scales are used with only early-phase validation, such as content or face validity. Other studies have discussed the reliability of these scales. However, the full validation process has not been discussed in any of the reviewed measurement scales. Conclusion: A reliable, fully validated measurement scale must be developed to assess the factors associated with the overuse of antibiotics. Identifying these factors will help to minimize the misuse of antibiotics.

Antibiotics overuse in children with upper respiratory tract infections in Saudi Arabia : risk factors and potential interventions

Background: Antibiotics misuse is currently one of the major public health issues worldwide. This misuse can lead to the development of bacterial resistance, increasing the burden of chronic diseases, rising costs of health services, and the development of side effects. Several factors may influence this pattern of overuse. Objectives:This article will review the pertinent factors contributing to the overuse of antibiotics worldwide, and to assess the intervention strategies to limit this overuse. Methods: studies about antibiotics use in children were reviewed from several electronic databases, such as MEDLINE and Pubmed. Results: Factors contributing to the overuse of antibiotics could include psychosocial factors, such as behaviors and attitudes (e.g. self-medication, over-the-counter medication, or patients/parents pressure), and demographic factors, such as socio-economic status and education level. Several intervention strategies were reported to be effective in reducing the overuse of antibiotics, such as health education, doctor-patient communication, and policies change. Multifaceted interventions were found to be the most effective in reducing the antibiotics overuse.