Quantitation of underivatized free amino acids in mammalian cell culture media using matrix assisted laser desorption ionization time-of-flight mass spectrometry

In this investigation, a quantitative matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) method was developed for the analysis of underivatized free amino acids in mammalian cell culture media. Calibration curves were developed for 12 amino acids over the linear range of 1-100 microM with coefficients of determination ranging from r2 = 0.9220 to r2 = 0.9973. An aerospray method was utilized for the sample deposition method, and the matrix, alpha-cyano-4-hydroxycinnamic acid, served as the internal standard. This assay was used to analyze bioreactor samples from five time points in the process. Concentrations determined through interpolation of the calibration curves were comparable to those obtained via reversed-phase HPLC based analysis with an average percent difference of 19.71%. Repeatability and intermediate precision studies were also performed, and the relative standard deviations ranged from 0.5943 to 21.41 and 3.157 to 18.97, respectively.     

Measuring individual and cultural differences in implicit trait theories.

A new measure of implicit theories or beliefs regarding the traitedness versus contextuality of behavior was developed and tested across cultures. In Studies 1 (N = 266) and 2 (N = 266), these implicit beliefs dimensions were reliably measured and replicated across U.S. college student samples and validity evidence was provided. In Study 3, their structure replicated well across an individualistic culture (the United States; N = 249) and a collectivistic culture (Mexico, N = 268). Implicit trait and contextual beliefs overlapped only modestly with implicit entity theory beliefs and were predicted by self-construals in ways that generally supported cultural psychology hypotheses. Implicit trait beliefs were fairly strongly endorsed in both cultures, suggesting that such beliefs may be university held. (PsycINFO Database Record (c) 2010 APA, all rights reserved)