Elucidation of the concise biosynthetic pathway of the communesin indole alkaloids

The communesins are a prominent class of indole alkaloids isolated from Penicillium species. Owing to their daunting structural framework and potential as pharmaceuticals, communesins have inspired numerous synthetic studies. However, the genetic and biochemical basis of communesin biosynthesis has remained unexplored. Herein, we report the identification and characterization of the communesin (cns) biosynthetic gene cluster from Penicillium expansum. We confirmed that communesin is biosynthesized by the coupling of tryptamine and aurantioclavine, two building blocks derived from L-tryptophan. The postmodification steps were mapped by targeted-gene-deletion experiments and the structural elucidation of intermediates and new analogues. Our studies set the stage for the biochemical characterization of communesin biosynthesis. This knowledge will aid our understanding of how nature generates remarkable structural complexity from simple precursors.

A contemporary series of patients undergoing open debridement for necrotizing pancreatitis

BACKGROUND

For patients with acute pancreatitis complicated by infected necrosis, minimally invasive techniques have taken hold without substantial comparison with open surgery. We present a contemporary series of open necrosectomies as a benchmark for newer techniques.

METHODS

Using a prospective database, we retrospectively identified consecutive patients undergoing debridement for necrotizing pancreatitis (2006 to 2009). The primary endpoint was in-hospital mortality.

RESULTS

Sixty-eight patients underwent debridement for pancreatic/peripancreatic necrosis. In-hospital mortality was 8.8% (n = 6). Infection (n = 43, 63%) and failure-to-thrive (n = 13, 19%) comprised the most common indications for necrosectomy. The false negative rate (FNR) for infection of percutaneous aspirate was 20.0%. Older age (P = .02), Acute Physiology and Chronic Health Evaluation II score upon admission (P = .03) or preoperatively (P < .01), preoperative intensive care unit admission (P = .01), and postoperative organ failure (P = .03) were associated with mortality.

CONCLUSIONS

Open debridement for necrotizing pancreatitis results in a low mortality, providing a useful comparator for other interventions. Given the high FNR of percutaneous aspirate, debridement should not be predicated on proven infection.

Expanding the structural diversity of polyketides by exploring the cofactor tolerance of an inline methyltransferase domain

A strategy for introducing structural diversity into polyketides by exploiting the promiscuity of an in-line methyltransferase domain in a multidomain polyketide synthase is reported. In vitro investigations using the highly-reducing fungal polyketide synthase CazF revealed that its methyltransferase domain accepts the nonnatural cofactor propargylic Se-adenosyl-l-methionine and can transfer the propargyl moiety onto its growing polyketide chain. This propargylated polyketide product can then be further chain-extended and cyclized to form propargyl-α pyrone or be processed fully into the alkyne-containing 4'-propargyl-chaetoviridin A.

Single-Institution Financial Analysis of Biologic Versus Synthetic Mesh Hernia Repair: A Retrospective Analysis of Patients Readmitted for Hernia Repair

The advent and proliferation of commercially available biologic mesh material has expanded the repertoire of hernia repair materials available to the surgeon. Given the higher initial cost of these mesh materials relative to synthetic materials such as polypropylene, there has been debate regarding the purported benefit of the use of biologic mesh. This study is a single-institution review of complex hernia repairs using both biologic and synthetic mesh materials. The patients included in the analyses were admitted to the institution at least twice for management of hernia; this permitted specific evaluation of a given diagnosis, hernia, in the same patient, but at different points in time. In a subset of patients, hernia repair was performed upon the second admission with conversion from biologic or synthetic mesh, which had been placed at the initial repair. The objective of this study was to evaluate the financial implications of mesh choice. Specific parameters reviewed included type of mesh used, total costs of hospitalization, direct cost associated with the hernia repair, total collections, and percentage of collections relative to total charges. Through such analysis, our aim was to determine whether there were any variances in revenue and costs associated with the application of either mesh material or the associated clinical scenarios.

EcdGHK are three tailoring iron oxygenases for amino acid building blocks of the echinocandin scaffold

The echinocandins are a small group of fungal N-acylated cyclic hexapeptides that are fungicidal for candida strains and fungistatic for aspergilli by targeting cell wall 1,3-β-glucan synthases. The side chains of all six amino acid building blocks have hydroxyl groups, including the nonproteinogenic 4R,5R-dihydroxy-Orn1, 4R-OH-Pro3, 3S,4S-dihydroxy-homoTyr4, and 3S-OH-4S-Me-Pro6. The echinocandin (ecd) gene cluster contains two predicted nonheme mononuclear iron oxygenase genes (ecdG,K) and one encoding a P450 type heme protein (ecdH). Deletion of the ecdH gene in the producing strain Emericella rugulosa generates an echinocandin scaffold (echinocandin D) lacking both hydroxyl groups on Orn1. Correspondingly, the ΔecdG strain failed to hydroxylate C3 of the homoTyr residue, and purified EcdG hydroxylated free L-homoTyr at C3. The ΔecdK strain failed to generate mature echinocandin unless supplemented with either 4R-Me-Pro or 3S-OH-4S-Me-Pro, indicating blockage of a step upstream of Me-Pro formation. Purified EcdK is a Leu 5-hydroxylase, acting iteratively at C5 to yield γ-Me-Glu-γ-semialdehyde in equilibrium with the cyclic imine product. Evaluation of deshydroxyechinocandin scaffolds in the in vitro anticandidal assays revealed up to a 3-fold loss of potency for the ΔecdG scaffolds, but a 3-fold gain of potency for the ΔecdH scaffold, in line with prior results on deoxyechinocandin homologues.

Identification and characterization of the chaetoviridin and chaetomugilin gene cluster in Chaetomium globosum reveal dual functions of an iterative highly-reducing polyketide synthase

We report the identification and characterization of the caz biosynthetic cluster from Chaetomium globosum and the characterization of a highly reducing polyketide synthase (PKS) that acts in both a sequential and convergent manner with a nonreducing PKS to form the chaetomugilin and chaetoviridin azaphilones. Genetic inactivation studies verified the involvement of individual caz genes in the biosynthesis of the azaphilones. Through in vitro reconstitution, we demonstrated the in vitro synthesis of chaetoviridin A from the pyranoquinone intermediate cazisochromene using the highly reducing PKS and an acyltransferase.

Interrupted Fischer indolization approach toward the communesin alkaloids and perophoramidine

A concise approach toward the total synthesis of the communesin alkaloids and perophoramidine is reported. The strategy relies on the use of the interrupted Fischer indolization to build the tetracyclic indoline core of the natural products. Studies to probe the scope and limitations of this plan are presented. Although the methodology does not tolerate a C8-allyl substituent en route to the challenging vicinal quaternary stereocenters, variation at C7 and on the C ring is permitted.

Allylic oxidations catalyzed by dirhodium caprolactamate via aqueous tert-butyl hydroperoxide: the role of the tert-butylperoxy radical

Dirhodium(II) caprolactamate exhibits optimal efficiency for the production of the tert-butylperoxy radical, which is a selective reagent for hydrogen atom abstraction. These oxidation reactions occur with aqueous tert-butyl hydroperoxide (TBHP) without rapid hydrolysis of the caprolactamate ligands on dirhodium. Allylic oxidations of enones yield the corresponding enedione in moderate to high yields, and applications include allylic oxidations of steroidal enones. Although methylene oxidation to a ketone is more effective, methyl oxidation to a carboxylic acid can also be achieved. The superior efficiency of dirhodium(II) caprolactamate as a catalyst for allylic oxidations by TBHP (mol % of catalyst, % conversion) is described in comparative studies with other metal catalysts that are also reported to be effective for allylic oxidations. That different catalysts produce essentially the same mixture of products with the same relative yields suggests that the catalyst is not involved in product-forming steps. Mechanistic implications arising from studies of allylic oxidation with enones provide new insights into factors that control product formation. A previously undisclosed disproportionation pathway, catalyzed by the tert-butoxy radical, of mixed peroxides for the formation of ketone products via allylic oxidation has been uncovered.

Comparison of water and lipid content measurements using diffuse optical spectroscopy and MRI in emulsion phantoms

We present a quantitative comparison of lipid and water signals obtained from broadband Diffuse Optical Spectroscopy (DOS) and Magnetic Resonance Imaging (MRI). DOS and MRI measurements were performed on an identical set of emulsion phantoms that were composed of different water/soybean oil fractions. Absolute concentrations of water and lipid ranging from 35-94% and 63-6%, respectively were calculated from quantitative broadband near-infrared (NIR) absorption spectra (650-1000 nm). MR images of fat and water were separated using the three-point Dixon technique. DOS and MRI measured water and lipid were highly correlated (R(2) = 0.98 and R(2) = 0.99, respectively) suggesting that these techniques are complementary over a broad range of physiologically relevant water and lipid values. In addition, comparison of DOS derived concentrations to the MRI "gold standard" technique validates our quantitation approach and permits estimation of DOS accuracy and sensitivity in vivo.

[Effects of synthetic interleukin-1 blockers on uveitis in rats]

OBJECTIVE

To investigate the therapeutic action of synthetic interleukin-1 blockers on uveitis in rats.

METHOD

Experiments were performed on 18 Spraque-Dawley rats (36 eyes), and the retinal interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) were quantified by an enzyme-linked immunoabsorbent assay (ELISA) before and after the rats with uveitis treated by synthetic interleukin-1 blockers.

RESULT

The retinal IL-1 beta and TNF-alpha in rats with uveitis treated by synthetic IL-1 blockers (CK-138, 139) were significantly decreased than those treated by contrasting design.

CONCLUSION

Synthetic IL-1 blockers (CK-138, 139) are effective in treatment of IL-1 alpha induced uveitis in the rat.