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Physicochemical Parameters Affecting the Electrospray Ionization Efficiency of Amino Acids after Acylation.

ABSTRACT: Electrospray ionization (ESI) is widely used in liquid chromatography coupled to mass spectrometry (LC-MS) for the analysis of biomolecules. However, the ESI process is still not completely understood, and it is often a matter of trial and error to enhance ESI efficiency and, hence, the response of a given set of compounds. In this work we performed a systematic study of the ESI response of 14 amino acids that were acylated with organic acid anhydrides of increasing chain length and with poly(ethylene glycol) (PEG) changing certain physicochemical properties in a predictable manner. By comparing the ESI response of 70 derivatives, we found that there was a strong correlation between the calculated molecular volume and the ESI response, while correlation with hydrophobicity (log P values), pKa, and the inverse calculated surface tension was significantly lower although still present, especially for individual derivatized amino acids with increasing acyl chain lengths. Acylation with PEG containing five ethylene glycol units led to the largest gain in ESI response. This response was maximal independent of the calculated physicochemical properties or the type of amino acid. Since no actual physicochemical data is available for most derivatized compounds, the responses were also used as input for a quantitative structure-property relationship (QSPR) model to find the best physicochemical descriptors relating to the ESI response from molecular structures using the amino acids and their derivatives as a reference set. A topological descriptor related to molecular size (SPAN) was isolated next to a descriptor related to the atomic composition and structural groups (BIC0). The validity of the model was checked with a test set of 43 additional compounds that were unrelated to amino acids. While prediction was generally good (R2 > 0.9), compounds containing halogen atoms or nitro groups gave a lower predicted ESI response.

SUBMITTER: Hermans J

PROVIDER: S-EPMC5588090 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Physicochemical Parameters Affecting the Electrospray Ionization Efficiency of Amino Acids after Acylation.

Hermans Jos J Ongay Sara S Markov Vadym V Bischoff Rainer R

Analytical chemistry 20170816 17

Electrospray ionization (ESI) is widely used in liquid chromatography coupled to mass spectrometry (LC-MS) for the analysis of biomolecules. However, the ESI process is still not completely understood, and it is often a matter of trial and error to enhance ESI efficiency and, hence, the response of a given set of compounds. In this work we performed a systematic study of the ESI response of 14 amino acids that were acylated with organic acid anhydrides of increasing chain length and with poly(et ...[more]

PMID: 28737384

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Project description:BACKGROUND: Colostrum has many beneficial effects on newborns due to its main compounds (proteins, fats, lactose, essential fatty acids, amino acids) as well as protective antibodies that confer to the body. The buffaloes are the second important species for milk production in the world after cows. The importance of the species is also conferred by a longer longevity, high dry content of milk and a strong organic resistance when compared with cows. The purpose of this study was to investigate the changes of buffalo colostrum compounds such as fatty acids, cholesterol and physicochemical parameters during the first seven days postpartum and under the impact of the season, summer on pasture and winter on dry diet (hay based). RESULTS: Fat from colostrum differs depending on the postpartum day showing mean values of 11.31-7.56% (summer season) and 11.22-7.51% (winter season). These values gradually decreased starting with first day postpartum until day seven. Dry substance and protein presented a similar evolution to fat reaching the lowest values at the end of the colostral period. Lactose, ash and pH showed a gradually increase reaching the maximum on day seven postpartum. The highest titres of fatty acids from colostrum are: butyric acid (C4:0), myristic acid (C14:0), palmitic acid (C16:0), oleic acid (C18:1) and the lowest values showed up in myristoleic acid (C14:1), cis-10-pentadecanoic acid (C15:1), pentadecylic acid (C15:0) and margaric acid (C17:0) for both seasons. Higher concentrations have been recorded for the summer season in general. Cholesterol concentration decreased from 12.93 and 12.68 mg/100 mL (summer and winter season) to 9.02 and 7.88 mg/100 mL in the end of the colostral period. CONCLUSIONS: Physicochemical compounds of buffalo colostrum were influenced by season and postpartum day of milking. Excepting lactose all other parameters gradually decreased during colostral period. Fatty acids and cholesterol showed the same evolution, presenting higher values for the summer season. Specific feeding in the summer season (on pasture) did lead in more concentrated colostrum in dry substance, fatty acids and cholesterol.

Dataset Information

Physicochemical Parameters Affecting the Electrospray Ionization Efficiency of Amino Acids after Acylation.

Publications

Physicochemical Parameters Affecting the Electrospray Ionization Efficiency of Amino Acids after Acylation.

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