Direct liquid introduction LC/MS microbore experiments for the analysis of nucleoside material present in human urine

In order to obtain detection limits low enough for the analysis of nucleoside material in biological samples, a direct liquid introduction (liquid chromatographic/mass spectrometric DLI) system was upgraded by inserting a self-built desolvation chamber between the DLI probe and the ion source and by switching to microbore high-performance liquid chromatography (HPLC) on a C-18 column. The system was evaluated for the analysis of pure nucleoside and 2'-deoxynucleoside compounds in CH3OH + H2O (80/20) and for the analysis of nucleoside mixtures which were separated using 0.01 M ammonium formate + methanol (97:3) as eluant. The detection of structurally important fragment ions in the lower mass region which could not be observed before and an enhanced sensitivity are considered to be the main improvements. In combination with an appropriate clean-up procedure the system was evaluated for the DLI liquid chromatographic/mass spectrometric analysis of some nucleosides present in a human urine sample. Pseudouridine and 5,6-dihydrouridine were detected and identified.     

Protection of 2,6-Diaminopurine 2′-Deoxyriboside

Abstract

Protection of both mine moieties of 2, 6-diaminopurine 2′-deoxyriboside as a dimethylformamidine group did not proove feasable, while protection with a phenoxyacetyl group afforded only a mono-protected analogue 5. This analogue can be incorporated into oligonucleotides without difficulties. However, oligonucleotides with diaminopurine substituted for adenine did not yield more stable duplexes for the two sequences tested here.     

Two new mutations in the sterol 27-hydroxylase gene in two families lead to cerebrotendinous xanthomatosis

This report concerns two new mutations in the sterol 27-hydroxylase gene in two patients with cerebrotendinous xanthomatosis (CTX). In a Surinam-Creole patient (patient A), a G deletion on position cDNA 546/547 in exon 3 led to a frameshift and the introduction of a premature termination codon. In a Dutch patient (patient B), a C→T transition at position 496 in exon 3 also led to a premature termination codon. Patient A was homozygous for the mutation, whereas patient B was compound heterozygous, a C→T transition also being found in exon 6 at position 1204. The two new mutations were confirmed by restriction analysis with the restriction enzymes FokI and MaeI, respectively. Received: 24 July 1996 / Revised: 9 August 1996     

Gehechtheid als beïnvloedende factor van gedrags- en psychologische symptomen bij dementie

Contemporary research has increasingly acknowledged the importance of attachment on stress-related processes in ageing. Congruent with this, there has been much research on attachment in older adults over the past three decades. In this article, the main findings of this research are summarized, with a focus on attachment and dementia. Results show that, in general, the number of attachment figures decreases in old age. Moreover, their identity changes as adult children, deceased loved ones and God become more prominent. With relation to the quality of attachment, anxiety in close relations appears to diminish as people age, while attachment avoidance remains relatively stable. Individuals with high levels of attachment security also report greater well-being and a more positive attitude towards ageing compared to persons with low levels of attachment security. Furthermore, individuals characterized by insecure attachment show more behavioral and psychological problems in dementia. Also, caregiver burden, depression, as well as the quality of care giving and future caregiver commitment differ depending on the quality of attachment of the caregiver. There is preliminary evidence for the efficacy of attachment-based interventions in dementia. Finally, there is a need for greater methodological uniformity and the use of measures that are validated for an older population.     

Genbank accession #: AJ237597

Plant Molecular Biology -     

The Electronic Nature of the Aglycone dictates the Drive of the Pseudorotational Equilibrium of the Pentofuranose Moiety in C-Nucleosides

Abstract

We herein show for the first time that the specific electronic character of a C-aglycone dictates the thermodynamic preference of the two-state N ? S pseudorotational equilibrium to either N- or S-type sugar. As the electron-deficiency of the C-aglycone increases, a more favourable O4′(n) → σ*(Cl'-C(sp2)) interaction results into anomeric stabilization as indicated by more positive ΔH° for the drive of the N ? S equilibrium to more N-type sugar conformation with pseudoaxial aglycone. Alternatively, as the C-aglycone becomes more electron-rich, an unfavourable O4′(n) → σ*(Cl'-C(sp2)) interaction results into anomeric destabilization as indicated by more negative ΔH° for the drive of the N ? S equilibrium to more S-type sugar conformation with pseudoequatorial aglycone.     

Measurement of individual angiotensin peptides by HPLC-RIA

Immunoreactive measurements of Angiotensin II in plasma, relate to a variety of angiotensin peptides with different biological activities. A method is described to differentiate these individual angiotensin peptides. It involves extraction of the peptides from plasma by reversible adsorption to phenylsilyl silica cartridges, separation by an isocratic, ion pairing high-pressure liquid chromatography technique and measurement of the appropriate fractions by radioimmunoassay. In umbilical venous plasma molar concentrations of the smaller angiotensin fragments were found to range between 16 and 25% of the concentrations of the angiotensin II octapeptide. Because some angiotensin antisera show higher affinity for the smaller peptides than for the octapeptide, concentrations of angiotensin II, measured by radioimmunoassay, may be overestimated by up to 35% unless the various angiotensin peptides are adequately separated.     

Retention of cryptic genes in microbial populations

Cryptic genes are silenced genes that can still be reactivated by mutation. Since they can make no positive contribution to the fitness of their carriers, it is not clear why many cryptic genes in microbial populations have not degenerated into useless DNA sequences. Hall et al. (1983) have suggested that cryptic genes have persisted because of occasional strong environmental selection for reactivated genes. The present mathematical study supports their suggestion. It shows that a cryptic gene can be retained without having any selective advantage over a useless DNA sequence, if selection for the reactivated gene occasionally occurs for a substantially long time.