1,411 research outputs found
Chemoenzymatic Synthesis of Cryptophycin Anticancer Agents by an Ester Bond-Forming Non-ribosomal Peptide Synthetase Module
Cryptophycins (Crp) are a group of cyanobacterial
depsipeptides with activity against drug-resistant tumors. Although they have been shown to be promising, further efforts are required to return these highly potent compounds to the clinic through a new generation of
analogues with improved medicinal properties. Herein,
we report a chemosynthetic route relying on themultifunctional enzyme CrpD-M2 that incorporates a 2-hydroxy acid moiety (unit D) into Crp analogues. CrpD-M2 is a unique nonribosomal peptide synthetase (NRPS) module comprised of condensation-adenylation-ketoreduction-thiolation (C-A-KR-T) domains. We interrogated A-domain 2-keto and 2-hydroxy acid activation and loading, and KR domain activity in the presence of NADPH and NADH. The
resulting 2-hydroxy acid was elongated with three synthetic
Crp chain elongation intermediate analogues through ester
bond formation catalyzed by CrpD-M2 C domain. Finally, the
enzyme-bound seco-Crp products were macrolactonized by
the Crp thioesterase. Analysis of these sequential steps was
enabled through LC-FTICR-MS of enzyme-bound intermediates
and products. This novel chemoenzymatic synthesis of
Crp involves four sequential catalytic steps leading to the
incorporation of a 2-hydroxy acid moiety in the final chain
elongation intermediate. The presented work constitutes the
first example where a NRPS-embedded KR domain is employed
for assembly of a fully elaborated natural product, and
serves as a proof-of-principle for chemoenzymatic synthesis of new Crp analogues
Comment on "Theory of tailoring sonic devices: Diffraction dominates over refraction"
Recently N. Garcia et al. (Phys. Rev. E 67, 046606 (2003)) theoretically
studied several acoustic devices with dimensions on de order of several
wavelenghts. The authors discussed on experimental results previously reported
by several of us (F. Cervera et al., Phys. Rev. Lett. 88, 023902 (2002)). They
concluded that diffraction and not refraction is the ominating mechanism that
explain the focusing effects observed in those experiments. In this Comment we
reexamined their calculations and discussed why some of their interpretations
of our results are misleading.Comment: 2 pages, 2 figures, a comment on an articl
Vaccines : A rapidly evolving technology - Are the hurdles being addressed?
AbstractVaccination usually works in infectious disease, why not in Cancer? Differences in the potency of microbial and cancer antigens, poor initiation of an immune response due to inadequate expression of tumour associated antigens, weak antigens or tolerance induction and local immune suppression were considered. There is a big difference between a therapeutic and a prophylactic vaccine.The opinion of the expert group was that an improved therapeutic efficacy can hardly be expected by further variation of types of vaccines, schedules, routes of administration and adjuvants alone. A major hurdle for developing therapeutic cancer vaccines is the need to effectively monitor the immune response and to be able to use this in an adaptive trial approach.End-points of assessment should be different from standard treatments as complete response or partial responses are usually low, unless combined with other therapies.In order to focus resources to overcome the hurdles of enhancing the therapeutic efficacy of cancer vaccines the Cancer Vaccine Clinical Trial Working Group, representing academia and the pharmaceutical and biotechnology industries has in a consensus process defined 'A clinical development paradigm for cancer vaccines and related biologics'
Semaphorin 6A knockout mice display abnormalities across ethologically-based topographies of exploration and in motor learning
Semaphorins are secreted or membrane-bound proteins implicated in neurodevelopmental processes of axon guidance and cell migration. Exploratory behaviour and motor learning was examined ethologically in Semaphorin 6A (Sema6A) mutant mice. The ethogram of initial exploration in Sema6A knockout mice was characterised by increased rearing to wall with decreased sifting; over subsequent habituation, locomotion, sniffing and rearing to wall were increased, with reduced habituation of rearing seated. Rotarod analysis indicated delayed motor learning in Sema6A heterozygous mutants. Disruption to the axonal guidance and cell migration processes regulated by Sema6A is associated with topographically specific disruption to fundamental aspects of behaviour, namely the ethogram of initial exploration and subsequent habituation to the environment, and motor learning
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