A comparison of the gas phase acidities of phospholipid headgroups: Experimental and computational studies

Proton-bound dimers consisting of two glycerophospholipids with different headgroups were prepared using negative ion electrospray ionization and dissociated in a triple quadrupole mass spectrometer. Analysis of the tandem mass spectra of the dimers using the kinetic method provides, for the first time, an order of acidity for the phospholipid classes in the gas phase of PE < PA << PG < PS < PI. Hybrid density functional calculations on model phospholipids were used to predict the absolute deprotonation enthalpies of the phospholipid classes from isodesmic proton transfer reactions with phosphoric acid. The computational data largely support the experimental acidity trend, with the exception of the relative acidity ranking of the two most acidic phospholipid species. Possible causes of the discrepancy between experiment and theory are discussed and the experimental trend is recommended. The sequence of gas phase acidities for the phospholipid headgroups is found to (1) have little correlation with the relative ionization efficiencies of the phospholipid classes observed in the negative ion electrospray process, and (2) correlate well with fragmentation trends observed upon collisional activation of phospholipid \[M - H](-) anions. (c) 2005 American Society for Mass Spectrometry.

End-of-life care in the intensive care unit : a systematic review of qualitative studies investigating the experiences and perceptions of the patient's family

Review question/objective The review objective is to synthesise the best available evidence on experiences and perceptions of family members of intensive care unit patients on the adequacy of end-of-life care, where life-support modalities have been withheld or withdrawn. Inclusion criteria Types of participants This review will consider studies that report on the experiences and perceptions of patients’ families on EOLC in the ICU, where life-support modalities have been withheld or withdrawn. The family is defined as “those who are closest to the patient... the family may include the biological family, family by acquisition, and the family of choice and friends”. Phenomena of interest The phenomena of interest for this review are the patients’ families experiences, perceptions or views on the adequacy of EOLC delivered in the ICU, where life-support modalities were withheld or withdrawn. These experiences may refer to the following views on domains of care considered important at the end-of-life in the ICU, which have been described already in the existing literature: timely, consistent, and compassionate communication, clinician availability, clinical decision making based on patients’ preferences, goals and values, physical care implemented to maintain patient comfort, holistic interdisciplinary care and bereavement care for families of patients who died.