Structure of the thiostrepton resistance methyltransferase.S-adenosyl-L-methionine complex and its interaction with ribosomal RNA.

The x-ray crystal structure of the thiostrepton resistance RNA methyltransferase (Tsr).S-adenosyl-L-methionine (AdoMet) complex was determined at 2.45-A resolution. Tsr is definitively confirmed as a Class IV methyltransferase of the SpoU family with an N-terminal "L30-like" putative target recognition domain. The structure and our in vitro analysis of the interaction of Tsr with its target domain from 23 S ribosomal RNA (rRNA) demonstrate that the active biological unit is a Tsr homodimer. In vitro methylation assays show that Tsr activity is optimal against a 29-nucleotide hairpin rRNA though the full 58-nucleotide L11-binding domain and intact 23 S rRNA are also effective substrates. Molecular docking experiments predict that Tsr.rRNA binding is dictated entirely by the sequence and structure of the rRNA hairpin containing the A1067 target nucleotide and is most likely driven primarily by large complementary electrostatic surfaces. One L30-like domain is predicted to bind the target loop and the other is near an internal loop more distant from the target site where a nucleotide change (U1061 to A) also decreases methylation by Tsr. Furthermore, a predicted interaction with this internal loop by Tsr amino acid Phe-88 was confirmed by mutagenesis and RNA binding experiments. We therefore propose that Tsr achieves its absolute target specificity using the N-terminal domains of each monomer in combination to recognize the two distinct structural elements of the target rRNA hairpin such that both Tsr subunits contribute directly to the positioning of the target nucleotide on the enzyme.

Semi-synthetic analogues of thiostrepton delimit the critical nature of tail region modifications in the control of protein biosynthesis and antibacterial activity.

We report the successful production of selectively-modified tail analogues of the natural product antibiotic thiostrepton, which have been used to evaluate the critical nature of this section of the antibiotic to its inhibition of protein synthesis. This work highlights the tail region as a critical area for future semi-synthetic or synthetically bioengineered thiostrepton derivatives.

The use of pentobarbital in cases of severe delirium: a case series.

Delirium is a common syndrome present at the end of life and causes significant distress for patients and families. Sleep disruption is a common precipitating factor for delirium and restoration of sleep may be instrumental in attenuating symptoms. In this cases series, we present three patients who were unresponsive to escalating doses of standard delirium medications, but whose delirium resolved once improved sleep was achieved using Pentobarbital. In a fourth patient, delirium was successfully treated where neuroleptics were contraindicated. Pentobarbital has been shown to reduce the time to sleep onset, decrease the number of body movements during sleep and spontaneous awakenings and increase the total sleep time. Pentobarbital may provide an additional treatment option for patients whose delirium is refractory to standard management approaches.

The impact of dreams of the deceased on bereavement: a survey of hospice caregivers.

Many recently bereaved persons experience vivid and deeply meaningful dreams featuring the presence of the deceased that may reflect and impact the process of mourning. The present study surveyed 278 bereaved persons regarding their own perspective of the relationship between dreams and the mourning process. Fifty eight percent of respondents reported dreams of their deceased loved ones, with varying levels of frequency. Most participants reported that their dreams were either pleasant or both pleasant and disturbing, and few reported purely disturbing dreams. Prevalent dream themes included pleasant past memories or experiences, the deceased free of illness, memories of the deceased's illness or time of death, the deceased in the afterlife appearing comfortable and at peace, and the deceased communicating a message. These themes overlap significantly with previous models of bereavement dream content. Sixty percent of participants felt that their dreams impacted their bereavement process. Specific effects of the dreams on bereavement processes included increased acceptance of the loved one's death, comfort, spirituality, sadness, and quality of life, among others. These results support the theory that dreams of the deceased are highly prevalent among and often deeply meaningful for the bereaved. While many counselors are uncomfortable working with dreams in psychotherapy, the present study demonstrates their therapeutic relevance to the bereaved population and emphasizes the importance for grief counselors to increase their awareness, knowledge, and skills with regards to working with dreams.

Progression of delirium in advanced illness: a multivariate model of caregiver and clinician perspectives.

BACKGROUND: Delirium is one of the most distressing and difficult to manage problems in advanced illness. Family caregivers have a unique view of the progression of delirium. OBJECTIVE: This study examined precursors to delirium from the perspective of family caregivers. DESIGN: This study utilized a two-stage concept mapping design that began with semistructured interviews with caregivers of patients suffering with delirium. The interview data was sorted and rated by clinicians prior to quantitative data analysis via multidimensional scaling (MDS) and cluster analysis. SUBJECTS/SETTINGS: The subjects were 20 family caregivers of patients with a diagnosis of delirium in a hospice inpatient unit. RESULTS: The main outcome of the study was a multidimensional model of precursors of delirium that included 99 specific items. The model included ten clusters within three general domains: Cognition, Distress, and Rest/Sleep. An exploratory analysis suggested that Rest and Sleep issues were evident to caregivers much earlier than other kinds of problems (mean=17.56 weeks prior to hospice admission, 95% CI=9.2-25.0 weeks). CONCLUSIONS: This study provides detailed insights from family caregivers about the progression of delirium. The caregiver observations were clustered by multivariate analysis to provide a map of symptom domains. The principal finding of this study is that sleep disturbance was identified by almost all family caregivers much earlier than other more commonly recognized symptoms associated with delirium. The study highlights the importance of sleep fragmentation in the temporal progression of delirium and points toward opportunities for improved measurement, prevention, and treatment.

Electronic structure calculations on the thiazole-containing antibiotic thiostrepton: molecular mechanics, semi-empirical and ab initio analyses.

Thiostrepton is a highly complex cyclic thiazoyl peptide antibiotic and is active against Gram-positive bacteria. Molecular mechanics, semi-empirical and ab initio studies were utilized to further understand the structural and electronic properties of this antibiotic.