Decay behavior of least-squares coefficients in auxiliary basis expansions.

Many quantum chemical methods, both wave function and density based, rely on an expansion of elements of the electron density in an auxiliary basis. However, little is known about the analytical behavior of the expansion coefficients and, in particular, about their rate of decay with distance. We discuss an exactly solvable model system and characterize the expansion coefficients for various fitting metrics and various dimensionalities of the auxiliary basis. In the case of Coulomb fitting, we find that the decay rate depends critically on the effective dimensionality D of the auxiliary basis, varying from O(r(-1)) to O(r(-3)) to O(e(-zetar)) for D = 1, 2, or 3.

Fragmentation of a novel marine peptide, plicatamide, involves an unusual gas-phase intramolecular rearrangement.

During our characterization of plicatamide 1, a modified octapeptide: Phe-Phe-His-Leu-His-Phe-His-dc deltaDOPA (where dc deltaDOPA = decarboxy-(E)-alpha,beta-dehydro-3,4-dihydroxyphenylalanine) from the blood cells of the ascidian Styela plicata, we noted a series of fragment ions from the [M + H]+ ion which could not be assigned. There was no evidence in the 1H NMR spectrum to support an alternative molecular structure and the series of fragment ions were not present in the tandem mass spectrometry analysis of the [M + Na]+ ion. In addition, there was no evidence that the sample was a mixture of isobaric compounds. We propose that an unusual C-terminal to N-terminal rearrangement is responsible for the series of fragment ions from the [M + H]+ ion. This rearrangement was not observed in peptide analogs of plicatamide which did not contain the dc deltaDOPA at the C-terminus suggesting that this moiety is critical for the rearrangement. The proposed reaction is analogous to that recently reported by Vachet et al. involving a fragment ion formed from leucine enkephalin.

Strain and sex differences in the morphology of the medial preoptic nucleus of mice.

The medial preoptic nucleus (MPO), which is involved in sexual and maternal behaviors, contains neuronal clusters that have been described as being sexually dimorphic in size and neuropeptide content in a variety of species. A subnucleus in DBA/2J (D2) inbred mice, called the pars compacta of the MPO (MPOpc), is absent in C57BL/6J (B6) inbred mice (Robinson et al. [1985] J. Neurogenet. 2:381-388). We report here on experiments that further characterize strain and sex differences in medial preoptic morphology in D2 and B6 inbred mice. A prominent MPOpc, located within the caudal part of the MPO and dorsal to the suprachiasmatic nucleus, was present in both male and female D2 animals but was absent from B6 animals. MPOpc neurons were darkly stained for Nissl substance and larger than neurons in the surrounding MPO. In D2 brains, galanin-immunoreactive (-ir), oxytocin-ir, vasopressin-ir, and NADPH diaphorase-positive neurons were concentrated within the MPOpc. Fewer similar neurons in the comparable region of the MPO of B6 mice suggests that the absence of the MPOpc is due to absence of these neurons rather than a less compact organization. In D2 animals, the density of galanin-ir neurons in the MPOpc was sexually dimorphic, with higher numbers of galanin-ir neurons in females. Strain differences in galanin-ir, oxytocin-ir, vasopressin-ir, and NADPH diaphorase staining appeared to be limited to the MPOpc. Cholecystokinin-immunoreactive neurons, which have been reported to be numerous in the sexually dimorphic central subdivision of the MPO of rats, were sparse in the MPO of D2 and B6 mice. Confirmation of the MPOpc as an accessory magnocellular neurosecretory nucleus was obtained by finding labeling of MPOpc neurons after injection of DiI into the posterior pituitary.

Styelin D, an extensively modified antimicrobial peptide from ascidian hemocytes.

We isolated styelin D, a 32-residue, C-terminally amidated antimicrobial peptide, from the blood cells (hemocytes) of the solitary ascidian, Styela clava. Styelin D had remarkably extensive post-translational modifications, containing two novel amino acids, dihydroxyarginine and dihydroxylysine, and two distinctly unusual ones, 6-bromotryptophan and 3,4-dihydroxyphenylalanine. In addition, the peptide exhibited microheterogeneity because of differential mono- and dihydroxylation of several lysine residues. The primary sequence of one variant was: GW(*)LR(**)K(**)AAK(**)SVGK(**)FY(*)Y(*)K(**)HK(*)Y(*) Y(*)IK(*)AAWQIG KHAL-NH(2), where W(*) is 6-bromotryptophan, R(**) is dihydroxyarginine, Y(*) is 3,4-dihydroxyphenylalanine, K(*) is 5-hydroxylysine, and K(**) is dihydroxylysine. Styelin D exhibited activity against Gram-negative and Gram-positive bacteria, and this activity was retained in 200 mm NaCl. The role of the extensive modifications may be to preserve activity at low pH and/or high salinity because, under these conditions, the native peptide was considerably more active against the Gram-positive bacterial strains than its unmodified synthetic analogue. The peptide was also hemolytic and quite cytotoxic to eukaryotic cells. These broad ranging activities, combined with its relative abundance in ascidian hemocytes, suggest that styelin D plays a significant role in the innate immune mechanisms of S. clava.

Plicatamide: A lead to the biosynthetic origins of the tunichromes?

Plicatamide is a modified octapeptide from the ascidian Styela plicata having the structure Phe-Phe-His-Leu-His-Phe-His-decarboxyDeltaDOPA (where decarboxyDeltaDOPA = decarboxy-(E)-alpha,beta-dehydro-3, 4-dihydroxyphenylalanine). Edman sequencing, tandem mass spectrometry, and proton NMR have been used to characterize 100 microg of the compound. Plicatamide represents an important link between two classes of biomolecules: the tunichromes which share an oxidatively decarboxylated C-terminus and higher molecular weight DOPA-polypeptides. The 8-residue sequence provides the first opportunity to investigate the biosynthetic origins of the tunichrome family by molecular biological techniques.

Mental health disaster response: nursing interventions across the life span.

In the aftermath of a natural disaster, adult survivors often move through the following phases of disaster response: Heroic Phase, Honeymoon Phase, Disillusionment Phase, and Reconstruction Phase. Understanding age-related responses to traumatic events such as a tornado enables mental health clinicians to individualize appropriate interventions and prevent or diminish emotional sequelae such as post-traumatic stress disorders. Psychiatric-mental health nurses are encouraged to attend local Red Cross disaster training to be prepared should the need arise for mobilization of mental health disaster response teams in your community.

Morulin Pm: a modified polypeptide containing TOPA and 6-bromotryptophan from the morula cells of the ascidian, Phallusia mammillata.

A novel polypeptide containing the unusual posttranslationally modified amino acids L-3,4,5-trihydroxyphenylalanine (TOPA) and L-6-bromotryptophan (6-BrW) has been isolated from the morula cells of the vanadium-accumulating ascidian, Phallusia mammillata. The polypeptide, designated Morulin Pm, has a molecular weight of 3825 +/- 0.6 and has a simple amino acid composition consisting mainly of TOPA and 6-BrW as well as Ser, Leu, Phe, and Ala. To our knowledge, this is the first reported example of multiple sites of brominated tryptophan in a polypeptide of this size. Edman degradation revealed the N-terminal sequence to be BrW-Leu-Phe-BrW before sequencing was blocked. While the N-terminal tripeptide could be isolated from chymotrypsin digests of Morulin Pm, the rest of the polypeptide resisted further cleavage by the proteases, a feature common among this class of peptides. However, unlike other ascidian blood cell peptides examined to date, microheterogeneity was minimal. For the first time a detailed NMR investigation could be undertaken on a member of this class of polypeptides. In addition to signals assignable to the constituent amino acids by extensive 2D experiments, resonances were present both in the 13C and 1H spectra not typical of a simple linear peptide. Two proton resonances were identified with a cross peak in the correlation spectrum strongly indicative of a C-terminal decarboxy-delta 2,3-unsaturated TOPA residue as observed in certain tunichromes and clionamide. Chemical degradation experiments were undertaken in an effort to produce identifiable fragments to which these signals could be assigned, including full and partial acid hydrolysis and tryptophan-targeted BNPS-skatole treatment. However, the nature of the modification remains unknown. Possible structures for the modification, which may represent the source of the difficulties encountered in the structural elucidation of this and related peptides, are assessed. Conjecture is made as to the biological relevance of Morulin Pm, based on its localization and chemical characteristics.

Novel 3,4-di- and 3,4,5-trihydroxyphenylalanine-containing polypeptides from the blood cells of the ascidians Ascidia ceratodes and Molgula manhattensis.

Acetic acid urea extraction of the blood cells of two ascidian species yielded four novel families of polypeptides (3500-5300 Da) containing 3,4-dihydroxyphenylalanine (DOPA) and 3,4,5-trihydroxyphenylalanine (TOPA) from the Phlebobranch Ascidia ceratodes and two DOPA proteins (9-10 kDa) from the Stolidobranch Molgula manhattensis. 3,4,5-Trihydroxyphenylalanine residues have not been found previously in polypeptides in any biological system. The DOPA content of the M. manhattensis proteins is the highest yet reported for a naturally occurring DOPA protein. The successful isolation of proteinaceous components from A. ceratodes blood cells requires the incorporation of high concentrations of complexing agent in the extraction buffers to inactivate vanadium(III) which forms intractable organometallic polymers. The A. ceratodes blood cell polypeptides are all rich in alanine and TOPA residues, have neutral to basic pI values, and, while all give single bands on acid urea-polyacrylamide electrophoresis, they exhibit extensive microheterogeneity. This is reflected by their large molecular weight distribution as determined by matrix-assisted laser desorption ionization-mass spectrometry, the variation in the ratio of their 280-nm absorption to chromophores of unknown structure in the polypeptide's electronic absorption spectra, and the N-terminal sequence analysis. The two M. manhattensis proteins consist largely of four amino acids (alanine, valine, phenylalanine, and DOPA) with DOPA accounting for upward of 40 mol%. Both give an N-terminus of Ala-Phe-Tyr before resisting further progress by Edman degradation. Proteins and polypeptides from both ascidians are extremely resistant to proteases, a property which, while hampering characterization by sequence analysis, appears ideally suited to their proposed function of forming an impervious hemostat at the site of vascular injury. The yield of proteins and polypeptides relative to tunichromes appears to be seasonally dependent. The presence of DOPA and TOPA moieties in the proteins and polypeptides implicates them, as well as the tunichromes, as potential metal-sequestering agents.

Vanadium in ascidians: changes in vanadium coordination and oxidation state upon cell lysis.

Changes in vanadium coordination during cell lysis have been followed by EPR spectroscopy of the blood cells of the phleborbranch ascidians Ascidia ceratodes and PHallusia julinea. The spectra obtained for A. ceratodes whole blood samples can be mainly ascribed to aquated oxovanadium(IV) in which the signals are broadened in freshly frozen blood relative to when the cells are lysed by thawing. The sources of this broadening are discussed and it is shown that the oxovanadium(IV) signal has its origin in a small percentage of damaged or lysed cells which release vanadium into a low sulfate, low acid environment in fresh samples. When thawed, the cells lyse releasing acid and sulfate into the environment of the oxovanadium(IV), with consequent narrowing of the EPR spectral linewidth. Freshly frozen P. julinea blood cell samples have EPR spectra with parameters intermediate between aquated oxovanadium(IV) and the "type I" parameters observed in a previous investigation of tissue samples of this species (S. G. Brand, C. J. Hawkins, A. T. Marshall, G. W. Nette, and D. L. Parry, Comp. Biochem. Physiol. 93B, 425 (1989)). A. ceratodes tissue samples also have EPR spectra that differ from that of the blood. It is suggested that EPR studies on tissue samples are more indicative of the resting state of vanadium in the cells as there is more physiological material to provide a pH buffering effect to stabilize the cells. Schemes are presented which incorporate all of the EPR observations in ascidian literature, where cellular lysis is proposed to be accompanied by vanadium undergoing oxidation and a series of chelate exchanges from a "type I" complex to aquated oxovanadium(IV). Protons released during these exchanges are suggested to provide the acidity characteristic of blood cell lysates. The biological implications of the concomitant release of vanadium and tunichrome (S. W. Taylor, D. L. Parry, C. J. Hawkins, and J. H. Swinehart, Comp. Biochem. Physiol. 106A, 531 (1993)) from the blood cells, to the process of wound repair are discussed.

Oxidation of peptidyl 3,4-dihydroxyphenylalanine analogues: implications for the biosynthesis of tunichromes and related oligopeptides.

The o-diphenolic amino acid L-3,4-dihydroxyphenylalanine (dopa), the enamine alpha,beta-dehydro-3,4-dihydroxyphenylalanine (delta-dopa), and/or hydroxylated derivatives thereof, are integrated into the primary sequence of many scleroproteins and polyphenolic oligopeptides such as the celenamides, tunichromes, and halocyamines. After oxidation of N-acetyldopa ethyl ester, a low mol wt analogue of peptidyl dopa, the resultant o-quinone tautomerized to (Z)-alpha,beta-dehydro-3,4-dihydroxyphenylalanine ethyl ester. We have characterized this delta-dopa derivative and an acetate 1,4-addition product formed during the synthesis. Tautomerization of peptidyl dopa quinone to delta-dopa may be involved in the biosynthesis of delta-dopa-containing oligopeptides.

Methotrexate-induced erythema multiforme.

The folic acid antagonist, methotrexate, has many applications in the treatment of neoplastic disease. While methotrexate produces several well-recognized toxic effects, cutaneous reactions are rare. A patient who developed classical erythema multiforme while receiving low-dose methotrexate as treatment of nonmetastatic gestational trophoblastic neoplasia is presented. Erythema multiforme has been associated with a variety of pharmacologic agents. It typically presents as a pruritic papular dermatitis of the extensor surfaces of the extremities and may require multiple skin biopsies to establish the diagnosis. Spontaneous reversal usually occurs with discontinuation of therapy. Patients developing erythema multiforme related to antineoplastic agents should be switched to an alternate regimen.

Exposure to carbon disulphide and ischaemic heart disease in a viscose rayon factory.

The cohort of viscose rayon workers previously described by Tiller et al has been reconstructed and followed up to the end of 1982. The pattern of mortality at ages 45 to 64 for the extended period 1950-82 is similar to that described by Tiller et al for 1950-64. The spinners, the workers most heavily exposed to carbon disulphide, have a significantly higher mortality from all causes than the least exposed group. The excess mortality is largely accounted for by ischaemic heart disease (IHD) for which the spinners have an SMR of 172. When mortality is related to an exposure score in the same group, both all cause (p less than 0.01) and IHD (p less than 0.001) mortality increase with increasing exposure level. When this analysis is repeated covering all ages these trends become much less strong and only that for IHD remains significant (p less than 0.05). Over the age of 65 there is a tendency for mortality to decline with increasing exposure. This is contrary to expectation under the usual hypothesis that carbon disulphide promotes atherosclerosis. Instead it suggests that carbon disulphide has some type of reversible, direct cardiotoxic or thrombotic effect. This is supported by the findings that there is a strong trend (p less than 0.01) for IHD mortality to increase with increasing exposure in the previous two years. Further, both IHD (p less than 0.001) and total (p less than 0.01) mortality show highly significant trends with exposure among current workers but no such trends among workers who have left the industry.