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The osmoprotectant 3-dimethylsulfoniopropionate (DMSP) occurs in Gramineae and Compositae, but its synthesis has been studied only in the latter. The DMSP synthesis pathway was therefore investigated in the salt marsh grass Spartina alterniflora Loisel.

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The resonance two-photon ionization (R2PI) spectra of the jet-cooled aniline dimers (An-d 0 ) 2 , (An-d 5 ) 2 , and (An-d 7 ) 2 have been recorded; the first 225 cm -1 region above the (An-d 0 ) 2 origin was also reproduced by fluorescence excitation spectroscopy. Relatively sharp structure near the origin of the local excited state is attributed to intermolecular modes, perhaps of multiple conformers. Broader features at higher energies are assigned to symmetric ring modes coupled to an underlying excimer state. The dispersed fluorescence spectrum excited at the dimer electronic origin suggests that excimer formation occurs soon after the local excited state is pumped. Molecular dynamics simulations support the inference from the spectroscopic observations that hydrogen bonding governs the structure of the aniline dimer.

The fragmentation of peptides, to which a positive charge is attached at the N-terminus, was studied by matrix-assisted laser desorption/ionization postsource decay mass spectrometry. In these experiments, the tris[(2,4,6-trimethoxyphenyl)phosphonium] acetyl group is covalently attached. The main advantage of this modification is that the resulting spectra are simplified and the fragment ions observed consist predominantly of a(n)-type ions. We report the results for charge-derivatized peptides formed following enzymatic digestion of phosphoenolpyruvate carboxykinase. Specific fragmentation of bonds within aspargine and threonine residues are observed and are discussed. The understanding of the mechanistic aspects of the fragmentation process is essential to formulate a simple and straightforward mass spectrometric strategy for peptide sequencing using these charged derivatives.

Reverse phase chromatography of the globin chains of adult, newborn, and fetal erythrocytes from three species of New World monkeys (Cebus apella, Aotus azarae, and Callithrix jacchus) representing three of the seven platyrrhine clades showed that gamma-globin expression was fetal in these animals. The globins were identified by a combination of chemical sequencing and mass spectrometric analysis. Since gamma-globin expression is fetal in the other major simian branch, the catarrhines, but embryonic in prosimian primates and nonprimate placental mammals, the evolution of fetal recruitment can now be assigned to the period between the simian-prosimian divergence (55 million years ago) and the platyrrhine-catarrhine divergence (35 million years ago). The gamma-globin gene underwent tandem duplication during the same evolutionary epoch, in accord with a model that suggests that the downstream duplicated gamma-gene (gamma2) was free to acquire the mutations necessary for fetal recruitment. Mass spectrometric analysis of tryptic digests of the gamma-globins verified the amino acid sequences deduced from genomic sequencing. Detailed analysis of high performance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry data showed that gamma2-globin in Cebus was expressed to a far greater extent than gamma1-globin, supporting inferences drawn from a study of the promoter sequences. A "pre-gamma"-globin was observed in C. apella and shown to be primarily the glutathionyl adduct. The other species, A. azarae and C. jacchus, also express only one gamma-globin polypeptide. This work provides biochemical evidence of an evolutionary trend in the platyrrhines to alter the duplicated gamma-globin gene locus so that only one gamma-globin polypeptide is expressed.

The expression of ϵ‐ and γ‐globin mRNA and protein has been determined in three Old World monkey species (Macaca mulatta, Macaca nemestrina, and Cercopithecus aethiops). Using RT‐PCR with primers for ϵ‐ and γ‐globin, both mRNAs were detected in early fetal stages, whereas at 128 days (85% of full term), only γ was expressed. High‐performance liquid chromatography was used for separation and quantitation, and matrix‐assisted laser desorption/ionization mass spectrometry was used for identification of globin polypeptides. An α‐globin polymorphism was observed in all of the species examined. During fetal life, γ‐globin was the predominant expressed β‐type globin. The red blood cells of infants still contained substantial amounts of γ‐globin, which declined to negligible levels in 14 weeks as β‐globin expression reached adult values. The ratio of γ1‐ to γ2‐globins (equivalent to Gγ/Aγ in humans) was approximately 2.5, similar to the Gγ/Aγ ratio observed in humans. Thus, γ‐globin gene expression in these Old World monkeys species has three features in common with human expression: expression of both duplicated γ genes, the relative preponderance of γ1 over γ2 expression, and the delay of the switch from γ‐ to β‐globin until the perinatal period. Thus, the catarrhines seem to share a common pattern of developmental switching in the β‐globin gene cluster, which is distinct from the timing of expression in either prosimians or the New World monkeys. Our results indicate that an Old World monkey, such as Rhesus, could serve as a model organism (resembling humans) for experimentally investigating globin gene expression patterns during the embryonic, fetal, and postnatal stages. J. Exp. Zool. (Mol. Dev. Evol.) 288:318–326, 2000. © 2000 Wiley‐Liss, Inc.

The electroreflectance (ER) spectra of an undoped-n+ type doped GaAs has been measured at various amplitudes of modulating fields (δF). Many Franz–Keldysh oscillations were observed above the band gap energy, thus enabling the electric field (F) in the undoped layer to be determined. The F is obtained by applying fast Fourier transformation to the ER spectra. When δF is small, the power spectrum can be clearly resolved into two peaks, which corresponds to heavy- and light-hole transitions. When δF is less than ∼1/8 of the built-in field (Fbi∼77 420 V/cm), the F deduced from the ER is almost independent of δF. However, when larger than this, F is increased with δF. Also, when δF is increased to larger than ∼1/8 of Fbi, a shoulder appears on the right side of the heavy-hole peak of the power spectrum. The separation between the main peak and the shoulder of the heavy-hole peak becomes wider as δF becomes larger.