Metal Stabilization of Collagen and de Novo Designed Mimetic Peptides.

We explore the design of metal binding sites to modulate triple-helix stability of collagen and collagen-mimetic peptides. Globular proteins commonly utilize metals to connect tertiary structural elements that are well separated in sequence, constraining structure and enhancing stability. It is more challenging to engineer structural metals into fibrous protein scaffolds, which lack the extensive tertiary contacts seen in globular proteins. In the collagen triple helix, the structural adjacency of the carboxy-termini of the three chains makes this region an attractive target for introducing metal binding sites. We engineered His3 sites based on structural modeling constraints into a series of designed homotrimeric and heterotrimeric peptides, assessing the capacity of metal binding to improve stability and in the case of heterotrimers, affect specificity of assembly. Notable enhancements in stability for both homo- and heteromeric systems were observed upon addition of zinc(II) and several other metal ions only when all three histidine ligands were present. Metal binding affinities were consistent with the expected Irving-Williams series for imidazole. Unlike other metals tested, copper(II) also bound to peptides lacking histidine ligands. Acetylation of the peptide N-termini prevented copper binding, indicating proline backbone amide metal-coordination at this site. Copper similarly stabilized animal extracted Type I collagen in a metal-specific fashion, highlighting the potential importance of metal homeostasis within the extracellular matrix.

Design of net-charged abc-type collagen heterotrimers.

Net-negatively-charged heterospecific A:B:C collagen peptide heterotrimers were designed using an automated computational approach. The design algorithm considers both target stability and the energy gap between the target states and misfolded competing states. Structural characterization indicates the net-negative charge balance on the new designs enhances the specificity of the target state at the expense of its stability.

A Case Report on Managing Hemolysis, Elevated Liver Enzymes, and Low Platelets (HELLP Syndrome) During a Rapid Response Code.

HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets) is a relatively rare condition that can complicate pregnancies. We present a 31-year-old gravida 5 para 0 female at 37-3/7 weeks gestation who presented with sudden onset severe epigastric pain, shortness of breath, diaphoresis, bradycardia, and elevated blood pressure. A Rapid Response Team (RRT) was called, and the patient was treated with IV magnesium in addition to blood pressure control medications. Laboratory results confirmed the diagnosis of HELLP syndrome. HELLP syndrome has the potential for major thrombotic complications and should be considered. Early consideration and evaluation of thrombotic complications amongst other common diagnoses are important for prompt treatment and optimization of maternal and fetal well-being.

An Atypical Case of Chilaiditi Syndrome.

Chilaiditi's sign is a rare radiological finding in which a portion of the colon or small intestine is interposed between the liver and right hemidiaphragm. We present a 28-year-old male who came to the emergency room with nausea and vomiting. A computed tomography scan without contrast of the abdomen and pelvis showed a new focus of air in the perihepatic region, suggesting a pneumoperitoneum or a loop of bowel. Exploratory laparotomy was pursued but deferred after a multi-disciplinary review of the imaging. A decision was made to pursue conservative management with a diagnosis of Chilaiditi syndrome. This case illustrates the importance of maintaining a broad differential when approaching a patient with abdominal distress and possible pneumoperitoneum, especially when the clinical picture does not align with radiological findings. Early consideration of Chilaiditi syndrome is important to minimize unnecessary surgical intervention such as laparotomy or further endoscopic intervention, which may lead to potential complications such as perforation, bowel wall ischemia, or respiratory failure.

Donor origin CAR T cells: graft versus malignancy effect without GVHD, a systematic review.

CD19, CD20 chimeric antigen receptor T (CAR T) cell therapy has shown promising results for the treatment of relapsed or refractory hematological malignancies. Best results have been reported in acute lymphoblastic leukemia patients with a complete response rate above 80%. Patients who received donor-derived CAR T cells for the relapsed malignancy after stem cell transplantation (allogenic hematopoietic stem cell transplant) were identified from the published trials. A total of 72 patients from seven studies were treated with donor-derived CAR T cells. Only five out of 72 patients (6.9%) developed graft versus host disease. Use of donor-derived CAR T cell for relapse prophylaxis, minimal residual disease clearance or salvage from relapse is therefore highly effective, and risk of graft versus host disease flare is very low. Side effects include cytokine release syndrome, tumor lysis syndrome, B-cell aplasia along with CNS toxicity.

Control of Collagen Stability and Heterotrimer Specificity through Repulsive Electrostatic Interactions.

Charge-pair interactions between acidic and basic residues on the surface of collagen can promote stability as well as control specificity of molecular recognition. Heterotrimeric collagen peptides have been engineered de novo using either rational or computational methods, which in both cases optimize networks of favorable charge-pair interactions in the target structure. Less understood is the role of electrostatic repulsion between groups of like charge in destabilizing structure or directing molecular recognition. To study this, we apply a "charge crowding" approach, where repulsive interactions between multiple aspartate side chains are found to destabilize the homotrimer states in triple helical peptide system and can be utilized to promote the formation of heterotrimers. Neutralizing surface charge by increasing salt concentration or decreasing pH can enhance homotrimer stability, confirming the role of charge crowding on the destabilization of homotrimers via electrostatic repulsion. Charge crowding may be used in conjunction with other approaches to create specific collagen heterotrimers.