Mass Spectrometric Analysis of Biological Molecules

The investigation of biological molecules through electrospray ionization mass spectrometry has expanded over the past 20 years. With a nanospray source allowing small volumes to be analyzed, perturbation of the sampled system is kept to a minimum. Two studies take advantage of the lack of perturbation to quantitate molecules within biological fluids. The first focuses on the concentration of glucose in tears. A quantitative method is developed to determine the concentration of glucose in human tears. Aqueous solutions of known glucose concentrations and induced tears are used to validate the method. Non-diabetic and diabetic subjects' tears are sampled. After overnight fasting, non-diabetic tear glucose concentration is shown to be 28 ± 14 μM. Tear glucose concentrations from samples taken before and after a meal are compared to the subjects' blood glucose concentrations. The second study that dealt with small biological fluid volumes sought to quantitate neuropeptides within a rat's cerebrospinal fluid. A tapered fused silica capillary is used to obtain cerebrospinal fluid in order to minimize damage to the brain. It was demonstrated that the matrix in the collected biological fluid caused the limit-of-quantitation of the method to be above the neuropeptide concentration within the sample.Protein-RNA complexes are also explored through ESI-MS. The observation of proteins and RNA is demonstrated. Further experiments are performed to determine how many monomers of neuroblastoma apoptosis-related protein bind to RNA during replication. In addition to these biological inquiries, a few silyl containing compounds are examined. Different ionization techniques and collision-induced-dissociation are used to characterize hexamethyldisiloxane, tert-butoxy trimethylsilane, and 2-trimethylsiloxy-propene to determine if they can differentiate volatile organic compounds. Collision-induced-dissocitaion of the silyl ions with argon, acetone-d6, and propanal as the collision gas provided structural identification and possible isomer discrimination. Results show that the ion originating from the loss of a methyl group from hexamethyldisiloxane can provide an avenue to distinguish between acetone and propanal