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INTRODUCTION: Mantle Cell Lymphoma (MCL) is a non-Hodgkin lymphoma accounting for 2.5% of lymphoid neoplasms in the United States. Primary gastrointestinal (GI) lymphomas account for 1-4% of all GI malignancies, with few reports of primary mantle cell lymphoma presenting as a single colonic mass and none to our knowledge with colon-colonic intussusception as the presenting finding. Accurate and timely diagnosis is imperative because MCL has rapid progression and early chemotherapeutic intervention results in improved patient outcomes. This work is reported in line with the SCARE criteria [1] for case report publication. PRESENTATION OF CASE: A 61-year-old male presented with 1 month history of nonspecific right sided abdominal pain. Computed Tomography (CT) of the abdomen identified an intussuscepting mass in the proximal ascending colon and an additional 8 mm hepatic lesion. Colonoscopy identified a large mass in the corresponding area of colon identified on CT. Histology and immunohistochemistry of biopsied specimen diagnosed MCL. DISCUSSION: Planned surgical intervention was deferred and the patient was referred for oncologic treatment. We report the first case to our knowledge of MCL presenting as colon-colonic intussusception and discuss the work-up of this rare lymphoma that clinicians may be required to diagnose and manage. CONCLUSION: This report serves as a reminder to maintain a broad differential inclusive of uncommon diseases and unanticipated pathology. Practicing with a thorough understanding of medical principles and clinical acumen is essential for optimal patient care and, as demonstrated in this case, preventing a potentially unnecessary surgical intervention thus delaying appropriate chemotherapy.
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Complete Boltzmann sampling of reaction coordinates in biomolecular systems continues to be a challenge for unbiased molecular dynamics simulations. A growing number of methods have been developed for applying biases to biomolecular systems to enhance sampling while enabling recovery of the unbiased (Boltzmann) distribution of states. The adaptive biasing force (ABF) algorithm is one such method and works by canceling out the average force along the desired reaction coordinate(s) using an estimate of this force progressively accumulated during the simulation. Upon completion of the simulation, the potential of mean force, and therefore Boltzmann distribution of states, is obtained by integrating this average force. In an effort to characterize the expected performance in applications such as protein loop sampling, ABF was applied to the full ranges of the Ramachandran φ/ψ backbone dihedral reaction coordinates for dipeptides of the 20 amino acids using all-atom explicit-water molecular dynamics simulations. Approximately half of the dipeptides exhibited robust and rapid convergence of the potential of mean force as a function of φ/ψ in triplicate 50 ns simulations, while the remainder exhibited varying degrees of less complete convergence. The greatest difficulties in achieving converged ABF sampling were seen in the branched-side chain amino acids threonine and valine, as well as the special case of proline. Proline dipeptide sampling was further complicated by trans-to-cis peptide bond isomerization not observed in unbiased control molecular dynamics simulations. Overall, the ABF method was found to be a robust means of sampling the entire φ/ψ reaction coordinate for the 20 amino acids, including high free-energy regions typically inaccessible in standard molecular dynamics simulations.