While tRNA and aminoacyl-tRNA synthetases are classes of biomolecules that have been extensively studied for decades, the finer details of how they carry out their fundamental biological functions in protein synthesis remain a challenge. Recent molecular dynamics (MD) simulations are verifying experimental observations and providing new insight that cannot be addressed from experiments alone. Throughout the review, we briefly discuss important historical events to provide a context for how far the field has progressed over the past few decades. We then review the background of tRNA molecules, aminoacyl-tRNA synthetases, and current state of the art MD simulation techniques for those who may be unfamiliar with any of those fields. Recent MD simulations of tRNA dynamics and folding and of aminoacyl-tRNA synthetase dynamics and mechanistic characterizations are discussed. We highlight the recent successes and discuss how important questions can be addressed using current MD simulations techniques. We also outline several natural next steps for computational studies of AARS:tRNA complexes.

Interactions between water and biomolecules can significantly change the former's structural, dynamic, and thermodynamic properties relative to the bulk. Experimental, theoretical, and computational studies show that changes in water properties can be observed at distances of more than 10 Å from a biomolecule. The effects of biopolymers on hydration water molecules can be attributed to several factors: the chemical nature of the amino acid residues involved, the spatial arrangement of the biomolecule, and its conformational flexibility. In the current study, we concentrate on the effect of protein chain flexibility on the properties of hydration water, using short peptides as a model. We constructed 18 linear peptides with the sequence (XXGG) × 5, where X represents one of the common amino acids, other than glycine and proline. Using molecular dynamics (MD) simulations, we studied how restricting the chain flexibility can affect the structural, dynamic, and thermodynamic properties of hydration water. We found that restricting the peptide dynamics can slow down the translational motions of water molecules to a distance of at least 12-13 Å. Analysis of the 'slow' water molecules (residence time ≥ 100 ps) together with a thermodynamic analysis of water within 4.5 Å of the peptide revealed significant differences between the hydration properties of the peptides. The balance between the entropic and enthalpic solvation effects defines the final contribution to the hydration free energy of the restricted system. Our study implies that different regions of the proteins that have different configurational entropies may also have different solvation entropies and therefore different contributions to the overall thermodynamic stability. Therefore, mutations of a solvent exposed residue may modify the thermodynamic stability depending solely on the flexibility of the mutated sites due to their different solvation characteristics.

Although the main features of the protein folding problem are coming into clearer focus, the microscopic viewpoint of nucleic acid folding mechanisms is only just beginning to be addressed. Experiments, theory, and simulations are pointing to complex thermodynamic and kinetic mechanisms. As is the case for proteins, molecular dynamics (MD) simulations continue to be indispensable tools for providing a molecular basis for nucleic acid folding mechanisms. In this review, we provide an overview of biomolecular folding mechanisms focusing on nucleic acids. We outline the important interactions that are likely to be the main determinants of nucleic acid folding energy landscapes. We discuss recent MD simulation studies of empirical force field and Go‐type MD simulations of RNA and DNA folding mechanisms to outline recent successes and the theoretical and computational challenges that lie ahead.

OBJECTIVE Infantile intracranial aneurysms are exceedingly rare. The goal of this study was to evaluate an institutional case series of infantile intracranial aneurysms, as well as those reported in the contemporary literature, to determine their demographics, presentation, management, and long-term outcome. METHODS A comprehensive literature review from 1980 to 2020 was performed to identify individual cases of intracranial aneurysms in the infantile population ≤ 2 years of age. Additional cases from the authors’ institution were identified during the same time period. An individual participant data meta-analysis (IPDMA) was performed, abiding by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Patient demographic, radiographic, and clinical information was obtained. Descriptive statistical data were recorded, and multivariate logistic regression analyses were performed. RESULTS Patient data were obtained for 133 patients from 87 articles in the literature. Ten additional patients at the authors’ institution were also identified, for a total of 143 patients included in the IPDMA. The majority (72.7%) of this cohort consisted of idiopathic aneurysms, while 13.3% were posttraumatic pseudoaneurysms, 9.8% were infectious mycotic aneurysms, and 4.2% were aneurysms associated with a systemic connective tissue disorder or vasculitis. The mean age at presentation was 6.6 months. The majority of infants (97.9%) harbored only 1 aneurysm, and hemorrhage was the most common presenting feature (78.3%). The mean aneurysm size was 14.4 mm, and giant aneurysms ≥ 25 mm comprised 12.9% of the cohort. Most aneurysms occurred in the anterior circulation (80.9%), with the middle cerebral artery (MCA) being the most commonly affected vessel (51.8%). Management strategies included open surgical aneurysm ligation (54.0%), endovascular treatment (35.0%), surgical decompression without aneurysm treatment (4.4%), and medical supportive management only (13.9%). Surgical aneurysm ligation was more commonly performed for MCA and anterior cerebral artery aneurysms (p = 0.004 and p = 0.015, respectively), while endovascular techniques were favored for basilar artery aneurysms (p = 0.042). The mean follow-up period was 29.9 months; 12.4% of the cohort died, and 67.0% had a favorable outcome (Glasgow Outcome Scale score of 5). CONCLUSIONS This study is, to the authors’ knowledge, the largest analysis of infantile intracranial aneurysms to date. The majority were idiopathic aneurysms involving the anterior circulation. Surgical and endovascular techniques yielded equally favorable outcomes in this cohort. Long-term outcomes in the infantile population compared favorably to outcomes in adults.

Cardiovascular system involvements have been frequently reported in hypermobile Ehlers‐Danlos Syndrome (hEDS). Mitral valve prolapse (MVP) and aortic root dilatation are included in the 2017 international classification criteria for hEDS. Different studies have found conflicting results regarding the significance of cardiac involvement in hEDS patients. We conducted a retrospective review of cardiac involvement in patients diagnosed with hEDS based on the 2017 International diagnostic criteria to provide further evidence toward more defined and reliable diagnostic criteria and recommended cardiac surveillance. A total of 75 hEDS patients with at least one diagnostic cardiac evaluation were included in the study. The most common reported cardiovascular complaints were lightheadedness (80.6%), followed by palpitations (77.6%), fainting (44.8%), and chest pain (32.8%). Of the 62 echocardiogram reports, 57 (91.9%) showed trace/trivial to mild valvular insufficiency, and 13 (21%) had additional abnormalities such as grade I diastolic dysfunction, mild aortic sclerosis, and trivial or small pericardial effusion. Of the 60 electrocardiograms (ECG) reports, 39 (65%) were normal, and 21 (35%) reported minor abnormalities or normal variants. Even though many hEDS patients in our cohort experienced cardiac symptoms, the presence of a significant cardiac abnormality was very low.