A soil test for improving N management is greatly needed in much of the Corn Belt. Relationships between yields of corn (Zea mays L.) grain and concentrations of nitrate in the surface l‐ft layer of soils when corn plants were 6 to 12 in. tall were studied across a total of 756 plots at several locations during 1985 and 1986 to evaluate the late‐spring soil test for nitrate. The time of sampling for this soil test represents a compromise between the need to sample late enough to reflect the effects of spring weather conditions on N availability but early enough so that supplemental N can be applied as a sidedressing if needed. A linear‐response‐and‐plateau (LRP) model showed that nitrate concentrations could explain 82% of the variability in relative yields (yields expressed as percentages of the highest yields observed within rotation‐site‐years) across all data collected. Although this model indicates that 21 ppm nitrate‐N in the surface l‐ft layer of soil is adequate to attain maximum yields, we suggest that a range of 20 to 25 ppm should be considered optimal. These findings indicate that this soil test offers great potential for improving N management in the Corn Belt. Amid mounting concerns that many farmers are applying more fertilizer than is desirable for environmental and (or) economic reasons, the most important use of the soil test may be to reduce excessive applications of fertilizer by showing when additional N is not needed.

A heme-binding protein (designated HBP23) has been purified from rat liver cytosol using heme-affinity chromatography and either reverse-phase high-performance liquid chromatography or sequential ion-exchange chromatography. The protein (23 kDa) binds heme with an affinity (Kd = 55 nM) higher than that of the abundant cytosolic heme-binding proteins, heme-binding protein (HBP)/liver fatty acid-binding protein (L-FABP) and the glutathione S-transferases (GSTs) (Kd = 100-200 nM). HBP23 is present in the cytosol of liver, kidney, spleen, small intestine, and heart, with the liver showing the highest content. A cDNA coding the 23-kDa protein was cloned using reverse transcription polymerase chain reaction with degenerative oligonucleotides derived from partial amino acid sequences. The cloned cDNA encoded 199 amino acids, and its amino acid sequence showed no homology to HBP/L-FABP, GSTs, or any other heme-binding proteins or hemeproteins. Homology search showed that HBP23 is highly homologous to mouse macrophage 23-kDa stress protein, which is inducible by oxidant stress in peritoneal macrophages [Ishii, T., Yamada, M., Sato, H., Matsue, M., Taketani, S., Nakayama, K., Sugita, Y., and Bannai, S. (1993) J. Biol. Chem. 268, 18633-18636]. Thioredoxin peroxidase as well as HBP23 and the mouse macrophage 23-kDa stress protein are members of the peroxiredoxin family, a recently recognized class of antioxidant proteins [Chae, H. Z., Chung, S. J., & Rhee, S. G. (1994) J. Biol. Chem. 269, 27670-27678]. An increase in HBP23 mRNA was observed in Hepa 1-6 cells after treatment with heme and cadmium and during liver regeneration after partial hepatectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

We report a general mass spectrometric approach for the rapid identification and characterization of proteins isolated by preparative two-dimensional polyacrylamide gel electrophoresis. This method possesses the inherent power to detect and structurally characterize covalent modifications. Absolute sensitivities of matrix-assisted laser desorption ionization and high-energy collision-induced dissociation tandem mass spectrometry are exploited to determine the mass and sequence of subpicomole sample quantities of tryptic peptides. These data permit mass matching and sequence homology searching of computerized peptide mass and protein sequence data bases for known proteins and design of oligonucleotide probes for cloning unknown proteins. We have identified 11 proteins in lysates of human A375 melanoma cells, including: a-enolase, cytokeratin, stathmin, protein disulfide isomerase, tropomyosin, Cu/Zn superoxide dismutase, nucleoside diphosphate kinase A, galaptin, and triosephosphate isomerase. We have characterized several posttranslational modifications and chemical modifications that may result from electrophoresis or subsequent sample processing steps. Detection of comigrating and covalently modified proteins illustrates the necessity of peptide sequencing and the advantages of tandem mass spectrometry to reliably and unambiguously establish the identity of each protein. This technology paves the way for studies of cell-type dependent gene expression and studies of large suites of cellular proteins with unprecedented speed and rigor to provide information complementary to the ongoing Human Genome Project.

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Structure and heterogeneity of the oligosaccharides from the lipopolysaccharides of a pyocin-resistant Neisseria gonorrhoeae ( Washington, DC 20307 Communicated by C. E. Ballou, August 22, 1988 (received for review June 1, 1988) ABSTRACTThe compositions and partial structures of the oligosaccharides from the lipopolysaccharides (LPS) of a pyocin-resistant Neisseria gonorrhoeae (strain JW31R) have been determined by liquid secondary ion mass spectrometry (LSIMS), tandem mass spectrometry, and methylation analysis. Four major structures were identified with Mr 2i23, 2000, 1961, and 1838, as well as seven species of lower abundance of Mr 1758-1272. The largest of the major oligosaccharides (Mr, 2122) consists of 3-deoxymanno-2-ketooctulosonic acid (KDO)-Hep2GaINAcGlcNAcGaI4Glc2 (Hep, heptose) and phosphoethanolamine (PEA). The smaller oligosaccharides are truncated versions of this larger oligosaccharide. The oligosaccharides consist of a common triantennary structure containing KDO at the reducing terminus attached to a heptose disaccharide. A hexose (Hex)2_3 branch is attached to the heptose linked directly to KDO and a GaINAc-Hex3, GlcNAc, and PEA are separately attached to the second heptose. These oligosaccharides are the first structures to be determined for a gonococcal LPS and should further our understanding of the structural and antigenic diversity of these glycolipids.Gonococcal disease is a major cause of morbidity worldwide, particularly in less developed countries where the disease often goes undetected and medical treatment is scarce. The situation is unlikely to improve since treatment ofgonococcal disease with antibiotics is becoming more difficult due to the emergence of resistant strains (1). This trend is particularly disturbing given the unexpectedly high incidence of positive human immunodeficiency virus antibody tests among people having venereal diseases (2). Clearly, an alternative approach to containing gonococcal disease, such as vaccination, would offer considerable advantages.The lipopolysaccharides (LPS) (7), a pyocin-resistant strain of N. gonorrhoeae, using a combination of liquid secondary ion mass spectrometry (LSIMS), tandem mass spectrometry, and methylation analysis. MATERIALS AND METHODSIsolation and Purification of the Oligosaccharides from JW-31R LPS. The LPS from a pyocin-resistant strain of N. gonorrhoeae were isolated and purified as described (8) and two oligosaccharide preparations (A and B) were then prepared. Preparation A was produced by first hydrolyzing 20 mg of LPS in 1% acetic acid for 2 hr at 100'C followed by centrifugation at 20,000 rpm (47,800 x g) for 20 min. The precipitate was then washed with H20 (3 x 5 ml, 20,000 rpm for 10 min), and the supernatant and the washings were pooled and lyophilized. The lyophilized oligosaccharides were dissolved in H20 (1 ml) and centrifuged, and the supernatant was again lyophilized. The oligosaccharide fraction was resuspended in 100 mM ammonium acetate (pH 7), centrifuged, and applied to a Bio-Gel P-4 colum...