Does the Nursing Care Plan help in the management of psychiatric risk?

The Nursing Care Plan (NCP) is routinely used to direct the nursing care of psychiatric in-patients, but the impact of NCPs on patient care and clinical outcome is not firmly established. NCPs from 246 patients, chosen at random from admissions to acute psychiatric wards, were analysed. The NCPs were scored for quality and also specifically for the presence of recorded risk assessment and appropriate level of nursing supervision. NCPs were evaluated in relation to psychiatric risk factors present prior to admission, and in relation to risk behaviour during hospitalization. Quality of NCP records was generally poor, with scores in all areas assessed being approximately half of the possible maximum. Patients with a perceived high risk of suicide prior to admission had significantly better NCP quality than other patients, but about a third of these high risk patients had no recorded risk assessment or supervision level in the nursing notes. Patients who had actually self-harmed within 4 weeks prior to admission were more likely to have a recorded risk assessment but did not score more highly than the rest of the patient population on any other measures of NCP quality. Patients who had made suicidal threats prior to admission but who were not deemed to be of high suicide risk before admission had significantly lower quality NCPs and were less likely to have a record of supervision level than the rest of the patients. The highest rate of supervision records occurred in patients who had shown dangerous behaviour prior to admission. Outcome in terms of two risk behaviours during admission (self-harm and violence) was not related to whether or not risk assessment and supervision levels had been recorded. Patients admitted compulsorily to hospital were more likely to have a supervision level recorded but were also more likely to abscond. It is concluded that issues of psychiatric risk were not adequately addressed in this sample of NCPs. Furthermore, the data raise serious questions about the usefulness of the NCP in helping to predict and prevent risky behaviour amongst psychiatric in-patients.

A proposed role for IF-3 and EF-T in maintaining the specificity of prokaryotic initiation complex formation.

Initiation factor-free 30S subunits of E. coli ribosomes bind aminoacyl-tRNAs more efficiently than fMet-tRNA(fMet). Elongator-tRNA binding was unaffected by IF-1 or IF-2 but was inhibited by IF-3. Their combination reduced this binding up to 40% and stimulated that of fMet-tRNA(fMet). Unexpectedly, EF-T also prevented elongator-tRNA binding by complexing both to the 30S and to the aminoacyl-tRNAs. Using AUGU3 as mRNA, elongator-tRNAs competed with fMet-fRNA(fMet) and with tRNA(fMet), fMet-tRNA(fMet) reacted with puromycin after addition of 50S subunits suggesting that it occupied the P site. EF-T directed binding of phe-tRNA to the 30S.AUGU3 complex at the A site only if fMet-tRNA(fMet) or tRNA(fMet) filled the P/E site. We propose that one function of EF-T may be to prevent the entry of aminoacyl-tRNAs into the 30S particle during initiation. The possibility that a special site for fMet-tRNA resides on 16S rRNA is also discussed.

Recognition of translational termination signals.

Ribosomes can specifically shift at certain codons so that the mRNA is read in two different reading frames. To determine if frameshifting occurs at the level of termination, polymers of defined sequence containing AUG, a coding sequence and an in- or out-of-phase nonsense codon were used to bind a termination substrate or to program synthesis and release of dipeptides in a highly purified in vitro translation system. fMet-tRNA bound to ribosomes with AUGUAA, AUGUAAn, AUGUUU, AUGUUA or AUGUAn was not a substrate for release factor RF-1. In contrast, AUGU1UAA, AUGU3UAAn, AUGU4UAAn, AUGU5UAAn effected RF-1-dependent release of fMet from ribosomes. This suggests that nonsense codons can stimulate release whether they occur in- or out-of-phase. Addition of exogenous UAA and RF-1 stimulated release with all oligonucleotides tested. Propagation restricted the RF-1-dependent recognition of out-of-phase nonsense codons but did not restrict recognition of in-phase UAA in AUGU3UAAn. Release of dipeptides from ribosomes programmed with AUGU4UAAn occurred without EF-G and with a mutant lacking EF-G activity, suggesting that out-of-phase termination can occur prior to translocation outside the ribosomal A-site. We propose that the ribosome X RF complex is required to complete proteins, but is also able to frameshift at a nonsense codon resulting in occasional out-of-phase termination of protein synthesis.

Improved free-energy parameters for predictions of RNA duplex stability.

Thermodynamic parameters for prediction of RNA duplex stability are reported. One parameter for duplex initiation and 10 parameters for helix propagation are derived from enthalpy and free-energy changes for helix formation by 45 RNA oligonucleotide duplexes. The oligomer sequences were chosen to maximize reliability of secondary structure predictions. Each of the 10 nearest-neighbor sequences is well-represented among the 45 oligonucleotides, and the sequences were chosen to minimize experimental errors in delta GO at 37 degrees C. These parameters predict melting temperatures of most oligonucleotide duplexes within 5 degrees C. This is about as good as can be expected from the nearest-neighbor model. Free-energy changes for helix propagation at dangling ends, terminal mismatches, and internal G X U mismatches, and free-energy changes for helix initiation at hairpin loops, internal loops, or internal bulges are also tabulated.

Free energy contributions of G.U and other terminal mismatches to helix stability.

Thermodynamic parameters of helix formation were measured spectroscopically for seven hexaribonucleotides containing a GC tetramer core and G.U or other terminal mismatches. The free energies of helix formation are compared with those for the tetramer core alone and with those for the hexamer with six Watson-Crick base pairs. In 1 M NaCl, at 37 degrees C, the free energy of a terminal G.U mismatch is about equal to that of the corresponding A.U pair. Although other terminal mismatches studied add between -1.0 and -1.6 kcal/mol to delta G0 37 for helix formation, all are less stable than the corresponding Watson-Crick pairs. Comparisons of the stability increments for terminal G.U mismatches and G.C pairs suggest when stacking is weak the additional hydrogen bond in the G.C pair adds roughly -1 kcal/mol to the favorable free energy of duplex formation.

Stability of XGCGCp, GCGCYp, and XGCGCYp helixes: an empirical estimate of the energetics of hydrogen bonds in nucleic acids.

The stabilizing effects of dangling ends and terminal base pairs on the core helix GCGC are reported. Enthalpy and entropy changes of helix formation were measured spectrophotometrically for AGCGCU, UGCGCA, GGCGCCp, CGCGCGp, and the corresponding pentamers XGCGCp and GCGCYp containing the GCGC core plus a dangling end. Each 5' dangling end increases helix stability at 37 degrees C roughly 0.2 kcal/mol and each 3' end from 0.8 to 1.7 kcal/mol. The free energy increments for dangling ends on GCGC are similar to the corresponding increments reported for the GGCC core [Freier, S. M., Alkema, D., Sinclair, A., Neilson, T., & Turner, D. H. (1985) Biochemistry 24, 4533-4539], indicating a nearest-neighbor model is adequate for prediction of stabilization due to dangling ends. Nearest-neighbor parameters for prediction of the free energy effects of adding dangling ends and terminal base pairs next to G.C pairs are presented. Comparison of these free energy changes is used to partition the free energy of base pair formation into contributions of "stacking" and "pairing". If pairing contributions are due to hydrogen bonding, the results suggest stacking and hydrogen bonding make roughly comparable favorable contributions to the stability of a terminal base pair. The free energy increment associated with forming a hydrogen bond is estimated to be -1 kcal/mol of hydrogen bond.

The tetraribonucleotide rCpGpCpG forms a left-handed Z-RNA double-helix.

NMR and circular dichroism studies show that the RNA tetranucleotide rCpGpCpG can form a Z-RNA left-handed double-helix. In 1.0 M NaClO4, circular dichroism measurements indicate that the tetramer is in the A-form. In 6.0 M NaClO4, there is a characteristic change in the circular dichroism, indicating that the tetramer adopts a left-handed Z-form. This conformation is verified by phosphorus and proton NMR studies. The 31P spectrum shows a large downfield shift in one of the resonances upon an increase in salt concentration. Proton nuclear Overhauser effect (NOE) experiments indicate that the guanosines are in the syn conformation. These results are consistent with the formation of a Z-form double-helix.

Improved free energies for G.C base-pairs.

Thermodynamic parameters of helix formation are reported for seven oligoribonucleotides containing only G.C pairs. These data are used with the nearest-neighbor model to calculate enthalpies and free energies of base-pair formation for G.C pairs. For helix initiation, the free energy change at 37 degrees C, delta G(0)37, is +3.9 kcal/mol; for helix propagation, the delta G(0)37 values are -2.3, -3.2 and -3.3 kcal/mol for C-G, G-G and G-C neighbors, respectively.

Contributions of dangling end stacking and terminal base-pair formation to the stabilities of XGGCCp, XCCGGp, XGGCCYp, and XCCGGYp helixes.

The role of stacking in terminal base-pair formation was studied by comparison of the stability increments for dangling ends to those for fully formed base pairs. Thermodynamic parameters were measured spectrophotometrically for helix formation of the hexanucleotides AGGCCUp, UGGCCAp, CGGCCGp, GCCGGCp, and UCCGGAp and for the corresponding pentanucleotides containing a 5'-dangling end on the GGCCp or CCGGp core helix. In 1 M NaCl at 1 X 10(-4) M strands, a 5'-dangling nucleotide in this series increases the duplex melting temperature (Tm) only 0-4 degrees C, about the same as adding a 5'-phosphate. In contrast, a 3'-dangling nucleotide increases the Tm at 1 X 10(-4) M strands 7-23 degrees C, depending on the sequence [Freier, S. M., Burger, B. J., Alkema, D., Neilson, T., & Turner, D. H. (1983) Biochemistry 22, 6198-6206]. These results are consistent with stacking patterns observed in A-form RNA. The stability increments from terminal A.U, C.G, or U.A base pairs on GGCC or a terminal U.A pair on CCGG are nearly equal to the sums of the stability increments from the corresponding dangling ends. This suggests stacking plays a large role in nucleic acid stability. The stability increment from the terminal base pairs in GCCGGCp, however, is about 5 times the sum of the corresponding dangling ends, suggesting hydrogen bonding can also make important contributions.

Parameters for the calculation of proton NMR chemical shifts of oligoribonucleotides.

A set of empirical parameters which allows the prediction of the proton NMR chemical shifts at 70 C of non-exchangeable heterobase and anomeric protons in oligoribonucleotides has been constructed. The set is based on the highly flexible nature of oligoribonucleotide single strands and the wide range of conformational states which can be populated at relatively high temperatures (70 C or greater). A pairwise subtractive procedure, using 129 ribonucleotide oligomers (all 16 dimers, all 64 trimers, 37 tetramers, and 12 pentamers), shows that significant contributions to the observed chemical shift of protons in a given nucleoside residue are made by first, second, and third neighbors on the 3' and the 5' sides. The majority of the neighbors cause shielding effects with the exception of some first neighbors on the 5' side of a given residue. The magnitude of the shielding effects is greatest for the purine heterobases and follows the order A greater than G greater than C greater than U, with first neighbors on the 3'side showing more pronounced effects than second neighbors and these in turn showing larger effects than third neighbors. Second neighbors on the 5' side showed consistently greater shieldings than first neighbors, a result attributed to the deshielding effects of the first 5' neighbor phosphate group. The parameter Tables are applied to the prediction of proton chemical shifts in one heptamer, four hexamers, and two pentamers and give average absolute differences between predicted and observed shifts less than 0.030 ppm. The parameter approach represents an excellent method of generating initial assignments of proton chemical shifts for any single strand oligoribonucleotide.

Effect of base sequence on in vitro protein-chain termination.

It has been proposed that the sequences surrounding nonsense codons determine the efficiency of protein-chain termination. To test this hypothesis, the termination factor, RF-1, was purified to near homogeneity and was used to examine the specificity of in vitro prokaryotic termination as a function of the nature and number of bases adjacent to UAA. Oligomers with different nucleotide sequences surrounding UAA were synthesized and their conformation was analyzed by NMR spectroscopy. The activity of these oligomers in RF-1-dependent termination was assayed by the release of analogues of peptides, N-acetyl or N-formyl-methionine, that were bound to ribosomes as N-acetyl or N-formyl-Met-tRNAfMet with either AUG or AUG covalently linked to another oligoribonucleotide. In the former case, a second oligomer was added to stimulate release. When added to the AUG-bound intermediate, UAAUAA was 5-fold less effective in stimulating release of N-acetyl-Met by RF-1 than were UAA, UAAN (where N is any base), UAAUGA, or UAAUAG. Oligomers AUGUAA, AUGUUAA, and AUG(U)mUAA18-25 (where m = 1-5) stimulated release by RF-1, whereas AUGCUA, AUGCUAA, and other control polymers were inactive. The data suggest that recognition of UAA depends, at least in part, on the nature of the bases surrounding UAA. A loosely stacked conformation of UAA in the short messengers favors termination, whereas nucleosides which encourage strong base stacking restrict release.

1H-nuclear magnetic resonance of intercalators and rGCA: a potential mutagenicity probe.

Variable temperature 1H-nuclear magnetic resonance (NMR) has been used to study the interaction of the RNA trimer, GpCpA, with the intercalators ethidium bromide and the acridine derivatives; proflavin, 9-amino-acridine, acridine orange, acridine yellow and acriflavin. The complexes formed were studied at nucleic acid to drug ratios of 1:1 and 5:1, the latter being useful in defining the effects of structural variation in the acridine series and in determining the site of intercalation. All the intercalators greatly stabilized the oligonucleotide duplex, the average melting temperature (Tm) increasing by up to 30 degrees C. Significant changes in individual Tms and chemical shifts were observed for all the GpCpA protons. 9-Amino-acridine and acriflavin did not stabilize the GpCpA duplex as substantially as the other acridine derivatives. It is suggested that this intercalator:GpCpA system, and its associated NMR-derived Tm, is a useful physical probe for potential mutagens.

Relative stability of guanosine-cytidine diribonucleotide cores: a 1H NMR assessment.

Proton NMR was used to study the secondary structure and melting behavior of six self-complementary oligoribonucleotide tetramers, each containing two guanosine and two cytidine residues (GGCC, CCGG, GCCG, CGGC, GCGC, and CGCG). GGCC and CCGG formed perfect duplexes containing four G.C base pairs with Tms of 54 and 47.8 degrees C, respectively; GCCG and CGGC formed staggered duplexes with two G.C base pairs and four 3' double-dangling bases, with Tms of 35.5 and 29.2 degrees C, respectively; GCGC formed a perfect duplex with a Tm of 49.9 degrees C, while CGCG formed a staggered duplex with a Tm of 36.9 degrees C. From these results, an order of stability of the cores containing two G.C base pairs was proposed: GC:GC is more stable than GG:CC which is more stable than CG:CG. The RY model for secondary structure stability prediction was applied to the above tetramers with reasonable success. Suggestions for refinements are discussed.

Prediction of 1H NMR chemical shifts of DNA oligomers.

A set of parameters, devised for the prediction of 1H NMR chemical shifts of heterobase and anomeric protons in the high temperature (greater than 70 degrees C) spectra of RNA oligomers has been found to be applicable to the corresponding DNA oligomers. Fifteen examples of DNA oligomers that have had high temperature spectra recorded and assigned show a mean absolute difference between predicted and assigned shifts of 0.045 ppm. The parameters for uridine H-5 are applied to the calculation of thymidine methyl group shifts and give excellent agreement with experimental assigned shifts. The RNA parameter set is a practical means of assigning heterobase and anomeric protons in DNA oligomers. A programme using the RNA parameter set has been written which enables the sequence of short DNA oligomers to be predicted from their 1H NMR spectra.

The effect of acceptor oligoribonucleotide sequence on the T4 RNA ligase reaction.

In order to make efficient use of T4 RNA ligase in a program involving chemical-enzymatic oligoribonucleotide synthesis, the sequence effects of the acceptor oligomer have been refined. The reaction of the donor molecules pCp and pUpUpUpCp with a series of trinucleoside diphosphates ApApN, CpNpA and NpCpA (where N = U, C, A or G) was examined. High-performance liquid chromatography was used for simultaneous analysis of all substrates, intermediates and products. For all trinucleoside bisphosphates tested a substantial amount of the intermediate A(5')pp(5')Cp or A(5')pp(5')UpUpUpCp was observed. This indicated that the extent of ligation was dependent upon sequence of the acceptor molecule and not upon adenylation of the donor. Conversely, examination of the four nucleoside 3',5'-bisphosphate donors pUp, pCp, pAp and pGp with a common acceptor ApApU indicated that in the case of poor ligation little of the intermediate adenylated donor was formed.

Effects of flanking G . C base pairs on internal Watson-Crick, G . U, and nonbonded base pairs within a short ribonucleic acid duplex.

A series of pentaribonucleotides, ApGpXpGpU (where X identical to A, G, C, or U), was synthesized to investigate the effects of flanking G . C pairs on internal Watson-Crick, G . U, and nonbonded base pairs. Sequences ApGpApCpU (Tm = 26 degrees C) and ApGpCpCpU (Tm = 25 degrees C) were each found to form a duplex with non-base-paired internal residues that stacked with the rest of the sequence but were not looped out. ApGpGpCpU also forms a duplex (Tm = 30 degrees C) but with dangling terminal nonbonded adenosines rather than internal nonbonded guanosines. ApGpUpCpU prefers a stacked single-strand conformation. In addition, contribution to duplex stability from an internal A . U or G . C base pair is enhanced by 6 degrees C when flanked by G . C base pairs as compared to A . U base pairs. G . C base pairs flanking an internal G . U base pair were found to be more tolerant to the altered conformation of a G . U pair and result in an increase to stability comparable with that found for an internal A . U base pair.