High-Throughput Detection of Thiamine Using Periplasmic Binding Protein-Based Biorecognition.

Although antibodies and aptamers are commonly used bioaffinity recognition elements, they are not available for many important analytes. As an alternative, we demonstrate use of a periplasmic binding protein (PBP) to provide high affinity recognition for thiamine (vitamin B1), an analyte of great importance to human and environmental health for which, like so many other small molecules, no suitable biorecognition element is available. We demonstrate that with an appropriate competitive strategy, a highly sensitive (limit of detection of 0.5 nM) and specific bioassay for thiamine and its phosphorylated derivatives can be designed. The high-throughput method relies upon the thiamine periplasmic binding protein (TBP) from Escherichia coli for thiamine biorecognition and dye-encapsulating liposomes for signal-enhancement. A thiamine monosuccinate-PEG-biotin derivative was synthesized to serve as an immobilized competitor that overcame constraints imposed by the deep binding cleft and structural recognition requirements of PBPs. The assay was applied to ambient environmental samples with high reproducibility. These findings demonstrate that PBPs can serve as highly specific and sensitive affinity recognition elements in bioanalytical assay formats, thereby opening up the field of affinity sensors to a new range of analytes.

An Extremely Rare Case of Rectal Signet Ring Cell Carcinoma.

Signet ring cell carcinoma of the rectum is a rare variant of colorectal cancer. When found, it is often diagnosed in late stages and has poor prognosis. This case depicts a patient with a history of Crohn's disease who presented to the hospital for perirectal abscesses. During the evaluation of both the abscesses and Crohn's disease, he was found to have stage IV adenocarcinoma with signet ring cell features. The patient was started on chemotherapy before surgical resection was considered, however, showed little response. The patient's family eventually pursued hospice care with comfort measures only. Colorectal signet ring cell carcinoma is rare but has poor prognosis as it is diagnosed generally at late and advanced stages. There is a need for more research in earlier detection of these rare cancers.

Ingested Potassium Chloride Pills on Imaging Misdiagnosed As Foreign Bodies in the Stomach: An Insight on Radiopaque/Hyperdense Substances in the Gastrointestinal Tract.

Foreign bodies are very common in the GI tract. Around 100,000 cases are reported each year in the United States. A total of 80% of those foreign body ingestions occur in the pediatric population. There are several reasons for foreign body impaction in the GI tract in adults. Psychiatric problems, anatomical abnormalities in the GI tract such as esophageal web, diverticula, stricture, and eating big food boluses are frequent causes of foreign body impaction in adults. Rarely do radio-opaque ingested materials appear as a foreign body in imaging studies. Such objects include several commonly used medications such as iron preparations, potassium chloride pills, amiodarone, spironolactone, bisoprolol, and lisinopril. Herein, we present one such case of potassium chloride pill ingestion, where it appeared as a foreign body in the stomach. However, on the endoscopic examination and repeat X-ray, the foreign body had been digested and disappeared.