Shotgun Lipidomics Identifies a Paired Rule for the Presence of Isomeric Ether Phospholipid Molecular Species

Ether phospholipids are abundant membrane constituents present in electrically active tissues (e.g., heart and the brain) that play important roles in cellular function. Alterations of ether phospholipid molecular species contents are associated with a number of genetic disorders and human diseases.Herein, the power of shotgun lipidomics, in combination with high mass accuracy/high resolution mass spectrometry, was explored to identify a paired rule for the presence of isomeric ether phospholipid molecular species in cellular lipidomes. The rule predicts that if an ether phospholipid A'-B is present in a lipidome, its isomeric counterpart B'-A is also present (where the ' represents an ether linkage). The biochemical basis of this rule results from the fact that the enzymes which participate in either the sequential oxidation of aliphatic alcohols to fatty acids, or the reduction of long chain fatty acids to aliphatic alcohols (metabolic precursors of ether lipid synthesis), are not entirely selective with respect to acyl chain length or degree of unsaturation. Moreover, the enzymatic selectivity for the incorporation of different aliphatic chains into the obligatory precursor of ether lipids (i.e., 1-O-alkyl-glycero-3-phosphate) is also limited.This intrinsic amplification of the number of lipid molecular species present in biological membranes predicted by this rule and demonstrated in this study greatly expands the number of ether lipid molecular species present in cellular lipidomes. Application of this rule to mass spectrometric analyses provides predictive clues to the presence of specific molecular species and greatly expands the number of identifiable and quantifiable ether lipid species present in biological samples. Through appropriate alterations in the database, use of the paired rule increases the number of identifiable metabolites in metabolic networks, thereby facilitating identification of biomarkers presaging disease states

Latent analysis of unmodified biomolecules and their complexes in solution with attomole detection sensitivity

The study of biomolecular interactions is central to an understanding of function, malfunction and therapeutic modulation of biological systems, yet often involves a compromise between sensitivity and accuracy. Many conventional analytical steps and the procedures required to facilitate sensitive detection, such as the incorporation of chemical labels, are prone to perturb the complexes under observation. Here we present a 'latent' analysis approach that uses chemical and microfluidic tools to reveal, through highly sensitive detection of a labelled system, the behaviour of the physiologically relevant unlabelled system. We implement this strategy in a native microfluidic diffusional sizing platform, allowing us to achieve detection sensitivity at the attomole level, determine the hydrodynamic radii of biomolecules that vary by over three orders of magnitude in molecular weight, and study heterogeneous mixtures. We illustrate these key advantages by characterizing a complex of an antibody domain in the solution phase and under physiologically relevant conditions.We would like to thank the ERC, BBSRC, Wellcome Trust, Newman Foundation, Winston Churchill Foundation, and Elan Pharmaceuticals for financial support. E.D.G was supported by the MRC (G1002272)

INFRARED SPECTROSCOPIC STUDY OF DERIVATIVES OF COBALT TRICARBONYL NITROSYL

Author Institution: Department of Chemistry, Princeton University“Infrared spectra in the CO and NO stretching region of mono and disubstituted derivatives of $Co(CO)_{3}N0$ in which CO is replaced by $PCl_{3}, PCl_{2} (C_{6}H_{5}), PCl(C_{6}H_{5})_{2}, P(C_{6}H_{5})_{3}$, p-tolyl isonitrile, t-butyl isonitrile and orthophenanthroline are recorded. The $\pi$-electron accepting abilities of coordinated CO and NO are compared and a ``spectrochemical series’’ for $\pi$-bonding ligands is proposed.

SOLVENT EFFECTS ON THE INFRARED FREQUENCY OF THE N-C BAND IN ISON1TRILES AND THE SIGN OF ∂μ/∂\partial \mu/\partial r

Author Institution: JR., Department of Chemistry, Princeton UniversitySpectra in the N-C stretching region are recorded for t-butyl and p-tolyl isonitriles in the vapor phase and in solution in 14 solvents. A number of solvents were found to shift the N -C band to frequencies higher than the vapor phase value. The N-C band shifts in solution correlate qualitatively with the theory of Drickamer and co-workers and allow us to assign a negative sign to $\partial_{\mu}/\partial_{r}$ for the N-C stretching vibration. A band at frequencies considerably higher than the vapor phase value is found for solutions of isonitriles in hydrogen -bonding solvents