A High-Throughput Continuous Spectroscopic Assay to Measure the Activity of Natural Product Methyltransferases.

Natural product methyltransferases (NPMTs) represent an emerging class of enzymes that can be of great use for the structural and functional diversification of bioactive compounds, such as the strategic modification of C-, N-, O- and S-moieties. To assess the activity and the substrate scope of the ever-expanding repertoire of NPMTs, a simple, fast, and robust assay is needed. Here, we report a continuous spectroscopic assay, in which S-adenosyl-L-methionine-dependent methylation is linked to NADH oxidation through the coupled activities of S-adenosyl-L-homocysteine (SAH) deaminase and glutamate dehydrogenase. The assay is highly suitable for a high-throughput evaluation of small molecule methylation and for determining the catalytic parameters of NPMTs under conditions that remove the potent inhibition by SAH. Through the modular design, the assay can be extended to match the needs of different aspects of methyltransferase cascade reactions and respective applications.

Mechanical properties of the beetle elytron, a biological composite material.

We determined the relationship between composition and mechanical properties of elytra (modified forewings that are composed primarily of highly sclerotized dorsal and less sclerotized ventral cuticles) from the beetles Tribolium castaneum (red flour beetle) and Tenebrio molitor (yellow mealworm). Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult eclosion, the elytron of Tenebrio is ductile and soft with a Young's modulus (E) of 44 ± 8 MPa, but it becomes brittle and stiff with an E of 2400 ± 1100 MPa when fully tanned. With increasing tanning, dynamic elastic moduli (E') increase nearly 20-fold, whereas the frequency dependence of E' diminishes. These results support the hypothesis that cuticle tanning involves cross-linking of components, while drying to minimize plasticization has a lesser impact on cuticular stiffening and frequency dependence. Suppression of the tanning enzymes laccase-2 (TcLac2) or aspartate 1-decarboxylase (TcADC) in Tribolium altered mechanical characteristics consistent with hypotheses that (1) ADC suppression favors formation of melanic pigment with a decrease in protein cross-linking and (2) Lac2 suppression reduces both cuticular pigmentation and protein cross-linking.

Anesthesia monitoring by registered nurses during cataract surgery: assessment of need for intraoperative anesthesia consultation.

PURPOSE: To assess the frequency and risk factors for intraoperative anesthesia consultation when performing cataract surgery monitored by registered nurses. SETTING: Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA. METHODS: This retrospective review was of 270 cataract surgeries performed under local anesthesia from April 1, 2002, to April 1, 2003. RESULTS: The American Society of Anesthesiologists (ASA) classification of each patient was determined: 1 patient was classified as ASA 1. One hundred fifty patients were classified as ASA 2. One hundred nineteen patients were classified as ASA 3. The anesthesiology department was consulted 24 times. Nineteen consultations involved patients who were ASA 3, and 5 consultations involved patients who were ASA 2 (P<.001). In most cases (23 of 24), the anesthesia service provided a consultation (eg, increase oxygen flow rate, clarification of electrocardiogram, start intravenous line, equipment repair) and left the nurses to continue to monitor the patient. In only 1 case (ASA 3), the anesthesia service converted the case to monitored anesthesia care and relieved the nurse to monitor the patient. CONCLUSIONS: In this study, monitoring of routine cataract surgery by registered nurses was associated with a low rate of intraoperative anesthesia consultation. Most consultations resulted in little intervention. The ASA classification appears predictive of the need for intraoperative anesthesia consultation.