Toehold clipping: A mechanism for remote control of DNA strand displacement.

The ability to create stimuli-responsive DNA nanostructures has played a prominent role in dynamic DNA nanotechnology. Primary among these is the process of toehold-based strand displacement, where a nucleic acid molecule can act as a trigger to cause conformational changes in custom-designed DNA nanostructures. Here, we add another layer of control to strand displacement reactions through a 'toehold clipping' process. By designing DNA complexes with a photocleavable linker-containing toehold or an RNA toehold, we show that we can use light (UV) or enzyme (ribonuclease) to eliminate the toehold, thus preventing strand displacement reactions. We use molecular dynamics simulations to analyze the structural effects of incorporating a photocleavable linker in DNA complexes. Beyond simple DNA duplexes, we also demonstrate the toehold clipping process in a model DNA nanostructure, by designing a toehold containing double-bundle DNA tetrahedron that disassembles when an invading strand is added, but stays intact after the toehold clipping process even in the presence of the invading strand. This work is an example of combining multiple physical or molecular stimuli to provide additional remote control over DNA nanostructure reconfiguration, advances that hold potential use in biosensing, drug delivery or molecular computation.

Locoregional Flap Reconstruction of the Distal Third of the Leg - What Role Does it Have in a Modern Reconstructive Algorithm?

ABSTRACT: Reconstruction of traumatic defects of the lower third of the leg poses a challenge due to limited locoregional options. Failed coverage can be associated with prolonged hospital stay, infection, loss of function, and unplanned return to surgery. Over the last few decades, free tissue transfer has dominated reconstructive algorithms for such defects; however, locoregional flaps may provide equally effective coverage in select patients. In the wake of the CODID-19 pandemic, locoregional flaps gained more consideration due to limited resources. We present a literature review and discussion of locoregional flaps, with emphasis on the quality and efficacy of these reconstructive modalities compared with free tissue transfer and surgical indications.Soleus flaps, reverse sural flaps, and cutaneous perforator-based flaps are workhorses for small to medium size defects of the distal third of the leg, even in the setting of concomitant orthopedic trauma and exposed vital structures. It is important to consider such alternatives an integral part of the reconstructive algorithm as they can provide durable coverage with a favorable complication profile with less resource utilization. Appropriate patient selection requires consideration of the character of the defect, smoking status, preexisting vascular disease, and the zone of injury.

Self-Assembly of DNA Nanostructures in Different Cations.

The programmable nature of DNA allows the construction of custom-designed static and dynamic nanostructures, and assembly conditions typically require high concentrations of magnesium ions that restricts their applications. In other solution conditions tested for DNA nanostructure assembly, only a limited set of divalent and monovalent ions are used so far (typically Mg2+ and Na+ ). Here, we investigate the assembly of DNA nanostructures in a wide variety of ions using nanostructures of different sizes: a double-crossover motif (76 bp), a three-point-star motif (~134 bp), a DNA tetrahedron (534 bp) and a DNA origami triangle (7221 bp). We show successful assembly of a majority of these structures in Ca2+ , Ba2+ , Na+ , K+ and Li+ and provide quantified assembly yields using gel electrophoresis and visual confirmation of a DNA origami triangle using atomic force microscopy. We further show that structures assembled in monovalent ions (Na+ , K+ and Li+ ) exhibit up to a 10-fold higher nuclease resistance compared to those assembled in divalent ions (Mg2+ , Ca2+ and Ba2+ ). Our work presents new assembly conditions for a wide range of DNA nanostructures with enhanced biostability.

Midwives' experiences of discussing health behaviour change within routine maternity care: A qualitative systematic review and meta-synthesis.

PROBLEM: Behaviours, such as smoking, alcohol use, unhealthy diet, lack of physical activity and vaccination non-adherence may lead to adverse pregnancy outcomes. BACKGROUND: Pregnancy has been identified as an opportune time for midwives to support women to make health behaviour changes. AIM: To synthesise existing qualitative research exploring midwives' experiences of discussing health behaviour change with women within routine care. METHODS: A systematic search was conducted across: Maternity and Infant Care, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, and Applied Social Sciences Index and Abstracts. Thematic analysis was used to synthesise the data. A professional and public advisory group provided feedback during the synthesis stage. FINDINGS: Twenty-two studies, published between 2005 and 2023, which represented findings from eight countries, were included in the review. The meta-synthesis revealed three themes: The midwife-woman relationship; Reflective and tailored behaviour change communication; Practical barriers to behaviour change conversations. This led to one overarching theme: Although midwives recognised the importance of behaviour change discussions, these conversations were not prioritised in clinical practice. CONCLUSION: Health behaviour change discussions were de-prioritised in midwives' clinical practice. Future research should explore intervention development to support midwives with their health behaviour change communication.

Switchback RNA.

Intricately designed DNA and RNA motifs guide the assembly of robust and functional nucleic acid nanostructures. In this work, we present a globally left-handed RNA motif with two parallel strands called switchback RNA and report its assembly, biophysical, and biochemical characterization. Switchback RNA can be assembled in buffers without Mg2+, with improved thermal stability in buffers containing Mg2+, Na+, or K+. Differences in the binding of small molecules to switchback RNA and conventional RNA indicate design-based approaches for small molecule loading on RNA nanostructures. Further, the differential affinity of the two component strands in switchback or conventional duplex conformations allows for toehold-less strand displacement. Enzyme studies showed that the switchback and conventional RNA structures have similar levels of nuclease resistance. These results provide insights for employing switchback RNA as a structural motif in RNA nanotechnology. Our observation that RNA strands with switchback complementarity can form stable complexes at low magnesium concentrations encourages studies into the potential occurrence of switchback RNA in nature.

The unusual structural properties and potential biological relevance of switchback DNA.

Synthetic DNA motifs form the basis of nucleic acid nanotechnology, and their biochemical and biophysical properties determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

The unusual structural properties and potential biological relevance of switchback DNA.

Synthetic DNA motifs form the basis of nucleic acid nanotechnology. The biochemical and biophysical properties of these motifs determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

Encoding, Decoding, and Rendering Information in DNA Nanoswitch Libraries.

DNA-based construction allows the creation of molecular devices that are useful in information storage and processing. Here, we combine the programmability of DNA nanoswitches and stimuli-responsive conformational changes to demonstrate information encoding and graphical readout using gel electrophoresis. We encoded information as 5-bit binary codes for alphanumeric characters using a combination of DNA and RNA inputs that can be decoded using molecular stimuli such as a ribonuclease. We also show that a similar strategy can be used for graphical visual readout of alphabets on an agarose gel, information that is encoded by nucleic acids and decoded by a ribonuclease. Our method of information encoding and processing could be combined with DNA actuation for molecular computation and diagnostics that require a nonarbitrary visual readout.

Fluorometric Determination of DNA Nanostructure Biostability.

The analysis and improvement of DNA nanostructure biostability is one of the keys areas of progress needed in DNA nanotechnology applications. Here, we present a plate-compatible fluorometric assay for measuring DNA nanostructure biostability using the common intercalator ethidium bromide. We demonstrate the assay by testing the biostability of duplex DNA, a double crossover DNA motif, and a DNA origami nanostructure against different nucleases and in fetal bovine serum. This method scales well to measure a large number of samples using a plate reader and can complement existing methods for assessing and developing robust DNA nanostructures.

Self-assembly of DNA nanostructures in different cations.

The programmable nature of DNA allows the construction of custom-designed static and dynamic nanostructures, and assembly conditions typically require high concentrations of magnesium ions which restricts their applications. In other solution conditions tested for DNA nanostructure assembly, only a limited set of divalent and monovalent ions have been used so far (typically Mg 2+ and Na + ). Here, we investigate the assembly of DNA nanostructures in a wide variety of ions using nanostructures of different sizes: a double-crossover motif (76 bp), a three-point-star motif (∼134 bp), a DNA tetrahedron (534 bp) and a DNA origami triangle (7221 bp). We show successful assembly of a majority of these structures in Ca 2+ , Ba 2+ , Na + , K + and Li + and provide quantified assembly yields using gel electrophoresis and visual confirmation of a DNA origami triangle using atomic force microscopy. We further show that structures assembled in monovalent ions (Na + , K + and Li + ) exhibit up to a 10-fold higher nuclease resistance compared to those assembled in divalent ions (Mg 2+ , Ca 2+ and Ba 2+ ). Our work presents new assembly conditions for a wide range of DNA nanostructures with enhanced biostability.

Behaviour change opportunities at mother and baby checks in primary care: a qualitative investigation of the experiences of GPs.

BACKGROUND: Pregnancy is widely recognised as a 'teachable moment' for healthy behaviour change and the postnatal period has been identified as the opportune time to initiate this change. In the UK, all women are offered a routine health check at 6-8 weeks postpartum with their GP. This provides a potential opportunity to facilitate long-term behaviour change discussions. AIM: To explore GPs' views and experiences of using the postnatal check as a health-related behaviour change opportunity. DESIGN AND SETTING: A qualitative, inductive study in general practice. METHOD: Semi-structured telephone interviews were conducted with 18 GPs. Audiorecorded interviews were transcribed verbatim and analysed using thematic analysis. RESULTS: One theme emerged from the data: the postnatal check is an unrealised opportunity to facilitate health-related behaviour change. This theme was organised into three subthemes: opportunity for health-related behaviour change; role responsibility; and patient-led versus GP-led behaviour change. CONCLUSION: Although GPs recognise the postnatal check as a potential opportunity for health-related behaviour change, it is underutilised as they do not perceive this to be the purpose of the check and are uncertain as to their role in facilitating lifestyle changes. To enable this long-term lifestyle behaviour change opportunity to be utilised more fully, further research is needed to understand women's expectations of the postnatal checks and the scope for further recommendations, guidance, and communication training around behaviour change.

Management of hyponatraemia in older people: old threats and new opportunities.

Hyponatraemia is the commonest electrolyte abnormality seen in clinical practice, and is especially prevalent in frail, older people. However, the serious implications of hyponatraemia in this age group are seldom recognized by clinicians. Hyponatraemia is associated with osteoporosis, impaired balance, falls, hip fractures and cognitive dysfunction. Even mild, apparently asymptomatic hyponatraemia is associated with prolonged stays in hospital, institutionalization and increased risk of death. Emerging evidence of the potential benefits of improved treatment of hyponatraemia is slowly generating renewed clinical interest in this area. The development of specific vasopressin-2 receptor antagonists (vaptans) has the potential to revolutionize the management of hyponatraemia, in particular for the syndrome of inappropriate antidiuretic hormone. However, challenges remain for the attending physician. Diagnosing the cause or causes of hyponatraemia in older people is difficult, and incorrect diagnosis can lead to treatment that worsens the electrolyte imbalance. Established treatments are often poorly tolerated and patient outcomes remain poor, and the role of vaptans in the treatment of older people is unclear. This review summarizes the existing evidence base and highlights areas of controversy. It includes practical guidance for overcoming some common pitfalls in the management of the elderly patient with hyponatraemia.