RNA G-quadruplex folding is a multi-pathway process driven by conformational entropy

The kinetics of folding is crucial for the function of many regulatory RNAs including RNA G-quadruplexes (rG4s). Here, we characterize the folding pathways of a G-quadruplex from the telomeric repeat-containing RNA by combining all-atom molecular dynamics and coarse-grained simulations with circular dichroism experiments. The quadruplex fold is stabilized by cations and thus, the ion atmosphere forming a double layer surrounding the highly charged quadruplex guides the folding process. To capture the ionic double layer in implicit solvent coarse-grained simulations correctly, we develop a matching procedure based on all-atom simulations in explicit water. The procedure yields quantitative agreement between simulations and experiments as judged by the populations of folded and unfolded states at different salt concentrations and temperatures. Subsequently, we show that coarse-grained simulations with a resolution of three interaction sites per nucleotide are well suited to resolve the folding pathways and their intermediate states. The results reveal that the folding progresses from unpaired chain via hairpin, triplex and double-hairpin constellations to the final folded structure. The two- and three-strand intermediates are stabilized by transient Hoogsteen interactions. Each pathway passes through two on-pathway intermediates. We hypothesize that conformational entropy is a hallmark of rG4 folding. Conformational entropy leads to the observed branched multi-pathway folding process for TERRA25. We corroborate this hypothesis by presenting the free energy landscapes and folding pathways of four rG4 systems with varying loop length.

Elderly and Patients with Large Breast Volume Have an Increased Risk of Seroma Formation after Mastectomy-Results of the SerMa Pilot Study

The collective of the SerMa pilot study included 100 cases of primary breast cancer or Carcinoma in situ who had undergone a mastectomy procedure with or without reconstruction of the breast using an implant or expander at Augsburg University Hospital between 12/2019 and 12/2022. The study aimed to investigate possible causes of seroma formation; reported here are the clinicopathological correlations between seroma formation and tumor biology and surgical procedures. Seroma occurred significantly more often in patients with older age (median patient age in cases with seroma was 73 years vs. 52 years without seroma; p < 0.001). In addition, patients with larger mastectomy specimen were significantly more likely to develop seroma (median ablation weight in cases with seroma 580 g vs. 330 g without seroma; p < 0.001). Other significant parameters for seroma formation were BMI (p = 0.005), grading (p = 0.015) and tumor size (p = 0.036). In addition, with insertion of implant or expander, a seroma occurred significantly less frequently (p < 0.001). In a binary logistic regression, age in particular was confirmed as a significant risk factor. In contrast, tumor biological characteristics, number of lymph nodes removed or affected showed no significant effect on seroma formation. The present study shows the need for patient education about the development of seroma in particular in older patients and patients with large breast volumes within the preoperative surgical clarification. These clinicopathological data support the previously published results hypothesizing that seroma formation is related to autoimmune/inflammatory processes and will be tested on a larger collective in the planned international multicenter SerMa study.

Continuous and interrupted abdominal-wall closure after primary emergency midline laparotomy (CONIAC-trial): study protocol for a randomised controlled single centre trial

INTRODUCTION

The optimal closure of the abdominal wall after emergency midline laparotomy is still a matter of debate due to lack of evidence. Although closure of the fascia using a continuous, all-layer suture technique with slowly absorbable monofilament material is common, complications like burst abdomen and hernia are frequent.

METHODS AND ANALYSIS

This randomised controlled trial with a 1:1 allocation evaluates the efficacy and safety of a continuous suture with or without additional interrupted retention sutures for closure of the abdominal fascia. Patients with an indication for a primary emergency midline laparotomy are eligible to participate in this study and will be randomised intraoperatively via block randomisation. Fascia closure in the intervention group will be done with a standard continuous suture with slowly absorbable monofilament material (MonoMax 1, B. Braun, Tuttlingen, Germany) and additional interrupted retention sutures every 2 cm of the fascia using rapidly absorbable braided material (Vicryl 2, Ethicon, Norderstedt, Germany). In the control group, the fascia is closed only with the standard continuous suture with slowly absorbable monofilament material. Sample size calculations (n=111 per study arm) are based on the available literature. The primary endpoint is the rate of dehiscence of the abdominal fascia (rate of burst abdomen within 30 days or rate of incisional hernia within 12 months). Secondary endpoints are wound infections, quality of life, length of hospital stay, morbidity and mortality. Patients as well as individuals involved in data collection, endpoint assessment, data analysis and quality of life assessment will be blinded.

ETHICS AND DISSEMINATION

The study protocol, the patient information and the informed consent form have been approved by the ethics committee of the Ludwig-Maximilians-University, Munich, Germany (reference number: 20-1041). Study findings will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

DRKS00024802.

WHO UNIVERSAL TRIAL NUMBER

U1111-1259-1956.

Virtual reality-based relaxation for enhancement of perioperative well-being and quality of life: protocol for a randomised pilot trial

INTRODUCTION

Patients with cancer undergoing surgery often suffer from reduced quality of life and various forms of distress. Untreated distress can negatively affect coping resources as well as surgical and oncological outcomes. A virtual reality-based stress reduction intervention may increase quality of life and well-being and reduce distress in the perioperative phase for patients with cancer. This pilot trial aims to explore the feasibility of the proposed intervention, assess patient acceptability and obtain estimates of effect to provide data for sample size calculations.

METHODS AND ANALYSIS

Patients with colorectal cancer and liver metastasis undergoing elective surgery will be recruited for this single-centre, randomised pilot trial with a three-arm design. A total of 54 participants will be randomised at 1:1:1 ratio to one of two intervention groups or a control receiving standard treatment. Those randomised to an intervention group will either receive perioperative virtual reality-based stress reduction exercises twice daily or listen to classical music twice daily. Primary feasibility outcomes are number and proportions of participants recruited, screened, consented and randomised. Furthermore, adherence to the intervention, compliance with the completion of the quality of life questionnaires and feasibility of implementing the trial procedures will be assessed. Secondary clinical outcomes are measurements of the effectiveness of the interventions to inform sample size calculations.

ETHICS AND DISSEMINATION

The study protocol, the patient information and the informed consent form have been approved by the ethics committee of the Ludwigs-Maximilians-University, Munich, Germany (Reference Number: 19-915). Study findings will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

DRKS00020909.