The physical path of sucrose unloading in the sugarcane stalk is described. About 50% of the vascular bundles in the internodes were located within 3 mm of the outside of the stalk. These bundles were inactive in long distance sucrose transport, as assessed by dye tracers of phloem flow. A sheath of fibres isolates the phloem apoplast from that of the storage parenchyma. In bundles associated with long distance transport (i.e. in the central region), the fibre sheath is narrowest to either side of the phloem fibre cap, and consists of living cells with plasmodesmata within pits in the secondary wall. Plasmodesmata were also arranged into pit fields between cells of the storage parenchyma. Since the vascular apoplast is isolated from the apoplast of the storage parenchyma, sucrose must move through the symplast of the fibre sheath. The calculated flux of sucrose through plasmodesmata of this cell layer was at the low end of reported values in the literature. Sucrose unloading within the storage parenchyma may also follow a symplastic route, with unloading into the apoplast of the storage parenchyma occurring as part of a turgor mechanism to increase sink strength.

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Recommendations for preparation of entry-level practitioners to work at all levels of the model are discussed.

The product ion spectra of approximately 200 dipeptides were acquired under low-energy conditions using a triple quadrupole mass spectrometer. The spectra of dipeptides containing an N-terminal arginine (R), histidine (H), or lysine (K) were observed to yield a b 1 ϩ H 2 O ion corresponding to the protonated basic amino acid. This was equivalent to the y 1 -ion in the corresponding C-terminal isomer. The formation of a b 1 ϩ H 2 O ion was not a significant fragmentation channel in any dipeptides analyzed including those containing a C-terminal basic amino acid unless they also contained an N-terminal basic amino acid. Occurring simultaneously and under equal energy conditions an apparent b 1 -ion was formed, which has its corresponding C-terminal equivalent in the y 1 -H 2 O ion. Energy resolved mass spectrometry (ERMS), deuterium labeling, and accurate mass experiments as well as data reported were used to show the relationships between the b 1 ϩH 2 O and b 1 -ions in the dipeptides containing an N-terminal basic amino acid and the y 1 and y 1 -H 2 O ions in the corresponding C-terminal isomers. (J Am Soc Mass Spectrom 2007, 18, 1414 -1422) © 2007 American Society for Mass Spectrometry C ollision induced dissociation (CID) in a triple quadrupole mass spectrometer utilizing electrospray ionization (ESI) is a widely used technique for obtaining product ion spectra for the characterization of peptides. The spectrometric information in the product ion spectrum acquired at a single collision energy is limited and can be significantly enhanced utilizing energy resolved mass spectrometry (ERMS), where product ion spectra are acquired at increasingly greater collision cell energies. This results in an increase in the internal energy of the precursor ion, which leads to further dissociation. A plot of relative intensity versus collision energy of selected fragment ions leads to the generation of breakdown curves [1,2]. Evaluation of these breakdown curves can provide information on fragmentation mechanisms such as distinguishing between competitive and consecutive fragmentation pathways, the stability of product ions, and identification of first and subsequent generation product ions [3][4][5][6][7][8]; identification of isomers and tautomers [9 -11]; and development of library searchable product ion spectra [12,13]. Since the internal energy of the precursor ion is not rigorously known, breakdown curves provide a qualitative picture of a fragmentation mechanism.Using these analytical tools, our laboratory analyzed ϳ200 dipeptides and have made some noteworthy observations in the product ion spectra of dipeptides containing N-terminal arginine (R), histidine (H), and lysine (K) and their C-terminal isomers. We used the single letter abbreviations for amino acids in dipeptides throughout this paper.The first was the observation of a fragment ion that corresponded to the mass of the protonated molecule (M ϩ H) ϩ of the basic amino acid. This was observed at m/z ϭ 175 for arginine, m/z ϭ 156 for histidine, and m/z ϭ 147 fo...

Commercial Cascarilla oil was fractionated by liquid chromatography on silica and alumina, and by preparative gas chromatography. On the basis of 1H‐NMR, 13C‐NMR, GC‐MS and GC‐FTIR data, 143 constituents were identified (75% of the oil). Five sesquiterpene hydrocarbons (II, III, V‐VII), a non‐terpenoid ester (VIII) and ketone (IX), two eudesmane alcohols (XI, XII), one sesquiterpene phenol (XIII), and a Clerodane diterpene (XIV) were new compounds. The stereochemistry of β‐cedren‐10‐ol (X), previously reported in Cascarilla, was also determined.

This research examined the relationship between race/ethnicity and rehabilitation outcomes as measured by closure status for VR consumers across two different target populations: persons with mental retardation and those who are deaf/hard-of-hearing. The researchers employed a meta-analysis to test the association between the predictor and criterion variables using select Rehabilitation Services Administration (RSA-911) driven studies. Data analyzed represent consumer case file information collected during the fiscal years of 1995-1996 through 1997-1998, the time period following passage of the 1992 Rehabilitation Act Amendments and implementation of the resulting Rehabilitation Cultural Diversity Initiative. The meta-analysis identified a significant relationship between race/ethnicity and closure status for each target population. African Americans with hearing loss and those with mental retardation were significantly less likely to achieve closure success when compared to Whites with respective disabilities. These findings and several implications for practice/service and disability policy are discussed.