Genetic Code Expansion of Mammalian Cells with Unnatural Amino Acids.

The expansion of the genetic code of mammalian cells enables the incorporation of unnatural amino acids into proteins. This is achieved by adding components to the protein biosynthetic machinery, specifically an engineered aminoacyl-tRNA synthetase/tRNA pair. The unnatural amino acids are chemically synthesized and supplemented to the growth medium. Using this methodology, fundamental new chemistries can be added to the functional repertoire of the genetic code of mammalian cells. This protocol outlines the steps necessary to incorporate a photocaged lysine into proteins and showcases its application in the optical triggering of protein translocation to the nucleus.

Light-cleavable rapamycin dimer as an optical trigger for protein dimerization.

Rapamycin-induced protein heterodimerization of FKBP12 and FRB is one of the most commonly employed switches to conditionally control biological processes. We developed an optically activated rapamycin dimer that does not induce FKBP12-FRB dimerization until exposed to light, and applied it to control kinase, protease, and recombinase function.

Signatures of recombination in clonal lineages of the citrus brown spot pathogen, Alternaria alternata sensu lato.

Most Alternaria spp. are considered asexual but recent molecular evolution analyses of Alternaria mating-type genes show that the mating locus is under strong purifying selection, indicating a possible role in sexual reproduction. The objective of this study was to determine the mode of reproduction of an Alternaria alternata sensu lato population causing citrus brown spot in central Florida. Mating type of each isolate was determined, and isolates were sequenced at six putatively unlinked loci. Three genetically distinct subpopulations (SH1, SH4A, and SH4B) were identified using network and Bayesian population structure analyses. Results demonstrate that most subpopulations of A. alternata associated with citrus are clonal but some have the ability to extensively recombine through a cryptic sexual cycle or parasexual cycle. Although isolates were sampled in close physical proximity (≈2,500-m² area), we were able to reject a random mating model using multilocus gametic disequilibrium tests for two subpopulations, SH1 and SH4B, suggesting that these subpopulations were predominantly asexual. However, three recombination events were identified in SH1 and SH4B and localized to individuals of opposite mating type, possibly indicating meiotic recombination. In contrast, in the third subpopulation (SH4A), where only one mating type was present, extensive reticulation was evident in network analyses, and multilocus gametic disequilibrium tests were consistent with recombination. Recombination among isolates of the same mating type suggests that a nonmeiotic mechanism of recombination such as the parasexual cycle may be operating in this subpopulation. The level of gene flow detected among subpopulations does not appear to be sufficient to prevent differentiation, and perhaps future speciation, of these A. alternata subpopulations.

A randomized trial comparing peripherally inserted central venous catheters and peripheral intravenous catheters in infants with very low birth weight.

BACKGROUND/PURPOSE: To determine whether percutaneously inserted central venous catheters (PICC) and peripheral intravenous catheters (PIV) in infants with very low birth weight (VLBW) differ with respect to (1) incidence of sepsis, (2) number of insertion attempts and catheters required for total intravenous therapy, (3) courses of antibiotics, and (4) total duration of intravenous (IV) use. METHODS: A randomized comparative trial was conducted involving 63 VLBW infants (<1,251 g) who required IV therapy. Infants were assigned randomly at 1 week of age to either a PIV or a PICC catheter and followed up prospectively until an IV was no longer required or the infant was transferred out of the neonatal intensive care unit. RESULTS: Data were analyzed on an intention-to-treat basis. There was no difference in the incidence of sepsis (P = .64), number of courses of antibiotics (P = .16), or total duration of IV use (P= .34) between the 2 groups. The number of insertion attempts required for total IV therapy was significantly lower in the PICC group than in the PIV group (P = .008). There also was a significantly lower number of total catheters utilized in the PICC group (P = .002). When data were controlled for birth weight strata the results were similar. CONCLUSION: PICC lines reduced the number of painful IV procedures in VLBW infants without additional morbidity.

A comparison of continuous infusion and intermittent flushing methods in peripheral intravenous catheters in neonates.

The purpose of this study was to compare two methods of maintaining peripheral intravenous devices in neonates: continuous infusion (CI) and intermittent flushing (IF). There was no significant difference in the mean duration of patency between the two groups, but there was a significant difference with respect to reasons for removal or loss of patency. The main reason for removal in the CI group was infiltration or phlebitis, and in the IF group the reason was occlusion.