Douglas F. Barofsky

Mass spectra of underivatized peptide amides related to substance P.

Abstract Mass spectra of underivatized hexa- and heptapeptide amides related to Substance P have been obtained with a conventional electron ionization mass spectrometer using sample vaporization from a tungsten wire by the technique of rapid heating, proton transfer ionization using ammonia, and photoplate recording of spectra. These spectra exhibit little evidence of sample pyrolysis and are readily interpreted to yield amino acid sequences.

Production and release of ions in the Fast Atom Bombardment ion source

Abstract FAB spectra have been obtained from several organic diammonium salts. The free dication was observed in only one case. Solid samples of the salts did not yield simply interpretable data. Mass spectra of the salts from a glycerol or glycerol/inorganic salt matrix exhibit several cation and anion related peaks as well as numerous singly charged fragment ions corresponding to charge separation, dealkylation, and elimination reactions accompanied by hydrogen transfer. These results point to low energy desorption pathways of preformed ions from immobile solid phases and mobile, concentrated liquid or high pressure gas phases.

Activation of field desorption emitters

Abstract Successful field desorption mass spectrometry requires a reliable means for wire emitter activation, i.e. growing semi-conducting micro-needles on the emitter surface. We have had difficulty in initiating needle growth and have overcome this problem by developing a simple process for controlled preroughening provides a large number of nucleation sites which have sufficient field strength to initiate needle growth. In addition to this technique a few observations concerning the use and performance of the emitters are discussed.

FAB and FD mass spectrometry of transition metal complexes

Abstract FD and FAB mass spectra were obtained for the first time from a number of cationic η3-allylic complexes of palladium and nickel. FD spectra are relatively easy to obtain; they are characterized by an intense cation and very few fragment ions. FAB spectra have, to date, been difficult to produce; they are characterized by a relatively small cation and numerous fragment ions. At present FD is the method of choice for rapid, relatively easy characterization of the molecular weight of the cation of these complexes.

Some experimental observations of liquid matrix effects in organic sims

Abstract At incident current densities on the order of 10−5A/cm2, a period of ∼1–30 s has been observed for nearly constant secondary ion emission to be established from glycerol sample matrices following the onset of sample irradiation with low energy (∼5–7 keV) metal ions. It is further observed that after prolonged irradiation the intensities of the molecular ions of certain compounds increase significantly shortly before the glycerol is depleted. Further study of these effects may assist in elucidating certain aspects of the matrixs role in the process of particle induced secondary ion emission from liquid samples.

Isolation of N-acetylaspartic acid from hypothalamic tissue and significance of its ACTH-releasing activity

Abstract During extensive fractionation of extractives of porcine hypothalami tissue, advanced steps were monitored by RIA for the activity of the corticotropin releasing factor (CRF). Two entities with CRF-activity were observed and identified. They were

Isolation of pyroglutamic acid from hypothalamic tissue and significance of its inhibition of prolactin release

Abstract Extensive fractionation of extractives of porcine hypothalamic tissue was scaled-up with the guidance of bioassays including the inhibition of prolactin release, because previously ca. ca.

Molecular sims with a liquid metal field ion point source

Abstract A liquid metal field lonizatlon (LMI) emitter is employed as the source for the primary beam in matrix assisted, molecular secondary ion mass spectrometry. Mass spectra produced from a number of representative organic compounds indicate that the LMI source has superior analytical potential in this application. Moreover, the point source characteristics of the LMI emitter could conceivably be exploited to permit localized, molecular analysis of biological tissue in combination with ion microscopy.