Mirror-image streptavidin with specific binding to L-biotin, the unnatural enantiomer.

The streptavidin-biotin system is known to have a very high affinity and specificity and is widely used in biochemical immunoassays and diagnostics. However, this method is affected by endogenous D-biotin in serum sample measurements (biotin interference). While several efforts using alternative high-affinity binding systems (e.g., genetically modified streptavidin and biotin derivatives) have been attempted, these efforts have all led to reduction in affinity. To solve this interference issue, the enantiomer of streptavidin was synthesized, which enabled specific binding to L-biotin. We successfully obtained a functional streptavidin molecule by peptide synthesis using D-amino acids and an in vitro folding technique. Several characterizations, including size exclusion chromatography (SEC), circular dichroism spectra (CD), and heat denaturation experiments collectively confirmed the higher-order enantiomer of natural streptavidin had been formed with comparable stability to the natural protein. L-biotin specific binding of this novel molecule enabled us to avoid biotin interference in affinity measurements using the Biacore system and enzyme-linked immunosorbent assay (ELISA). We propose the enantiomer of streptavidin as a potential candidate to replace the natural streptavidin-biotin system, even for in vivo use.

Quantification of Amyloid-ß in Plasma by Simple and Highly Sensitive Immunoaffinity Enrichment and LC-MS/MS Assay.

BACKGROUND: Numerous immunoassays have been developed to quantify amyloid ß1-40 (Aß40) and amyloid ß1-42 (Aß42). Nevertheless, given the low concentration of Aß and the high levels of interfering factors in plasma, quantification of plasma Aß is still challenging. To overcome the problems related to the specificity of Aß immunoassays, this study aimed to develop an immunoaffinity enrichment and LC-MS/MS (IA-MS) assay. METHODS: We developed an IA-MS assay using antibody-labeled magnetic beads for purification and LC-MS/MS for Aß quantification. To avoid the loss of Aß due to aggregation in acidic buffer, we used alkaline elution buffer for immunoaffinity enrichment. The concentrations of the Aßs in plasma samples were measured, and the correlation between the plasma and cerebrospinal fluid (CSF) Aß42/Aß40 ratio was also evaluated. RESULTS: The intensities of the Aß mass peaks were significantly higher with the alkaline elution buffer than with the acidic elution buffer (Aß40: 3.6-fold, Aß42: 5.4-fold). This assay exhibited high reproducibility (intra-assay and inter-assay precision, %CV <15), and the working ranges of Aß40 and Aß42 were determined to be 21.7 to 692.8 pg/mL and 5.6 to 180.6 pg/mL, respectively. The concentrations of Aß40 and Aß42 in plasma were measured by IA-MS, and the plasma Aß42/Aß40 ratio was correlated with the CSF Aß42/Aß40 ratio (rs = 0.439, P < 0.01). CONCLUSIONS: The IA-MS assay has sufficient analytic performance for measuring endogenous Aß40 and Aß42 in plasma. This assay can lead to new lines of clinical discovery related to amyloid pathology.

Usefulness of plasma full-length glypican-3 as a predictive marker of hepatocellular carcinoma recurrence after radial surgery.

Predicting the risk of hepatocellular carcinoma (HCC) recurrence before treatment is necessary for developing subsequent treatment policies. Several tumor markers found in blood, such as alpha-fetoprotein (AFP) and protein induced by vitamin K absence or antagonist-II (PIVKA-II), are presently used to determine the occurrence and recurrence of HCC and to predict patient prognosis. However, these markers are insufficient for these purposes as certain patients have HCC recurrence despite exhibiting negative AFP and PIVKA-II. The present study identified glypican-3 (GPC3), an embryonal carcinoma antigen that is expressed specifically in HCC and is secreted into blood. Although the N-terminal domain of GPC3 in sera may be a potential prognostic factor for HCC, its biological role remains unclear. By contrast, full-length GPC3 (FL-GPC3) is reported to serve important roles in cell differentiation, proliferation and signaling events that cause HCC. Given the biological roles of FL-GPC3 in HCC progression, the present study evaluated its potential as a predictive marker of HCC recurrence. In the present study, a novel measurement system was constructed to specifically measure plasma FL-GPC3. Subsequently, its ability to predict recurrence after radical surgery in 39 HCC patients was evaluated. The results revealed that preoperative FL-GPC3 levels in patients with recurrence were significantly higher than those in patients without recurrence, suggesting that FL-GPC3 could be a better predictive maker of risk of recurrence than AFP or PIVKA-II. Furthermore, it was determined that the combination of FL-GPC3, AFP and PIVKA-II could predict recurrence within one year of radical surgery with high sensitivity and specificity. Based on these results, the validation of FL-GPC3 as a predictive marker of HCC recurrence in a larger population is warranted.

Plasma and tumoral glypican-3 levels are correlated in patients with hepatitis C virus-related hepatocellular carcinoma.

Glypican-3 (GPC3) is a cancer antigen expressed in approximately 80% of hepatocellular carcinomas (HCC) and is secreted into the blood. To confirm the effectiveness of GPC3 as a biomarker in HCC, we analyzed the relationship between GPC3 expression levels in cancer cells and in blood in 56 patients with HCC. Preoperative plasma GPC3 levels were determined with an immunoassay, and expression of GPC3 in resected tumors was analyzed by immunohistochemical staining. Median plasma GPC3 level in all HCC cases was 4.6 pg/mL, and tended to be higher in patients with hepatitis C virus (HCV)-related HCC (HCV group) (9.9 pg/mL) than in patients with hepatitis B virus (HBV)-related HCC (HBV group) (2.6 pg/mL) or in those without virus infection (None group) (3.0 pg/mL), suggesting that the virus type most likely influences GPC3 secretion. Median percentage of GPC3+ cells in tumors was also higher in the HCV (26.2%) and HBV (11.1%) groups than in the None group (4.2%). In the HCV group, there was a positive correlation between the two parameters (r = 0.66, P < .01). Moreover, receiver operating characteristic analysis predicted >10% GPC3+ cells in a tumor if the cut-off value was 6.8 pg/mL (sensitivity 80%, specificity 100%; area under the curve 0.875, 95% confidence interval 0.726-1) in the HCV group. Plasma concentration of GPC3 could be a predictive marker of tumoral GPC3 expression in patients with HCV-related HCC, suggesting a useful biomarker for immunotherapies targeting GPC3, although larger-scale validations are needed.

Diversity in protein profiles of individual calcium oxalate kidney stones.

Calcium oxalate kidney stones contain low amounts of proteins, some of which have been implicated in progression or prevention of kidney stone formation. To gain insights into the pathophysiology of urolithiasis, we have characterized protein components of calcium oxalate kidney stones by proteomic approaches. Proteins extracted from kidney stones showed highly heterogeneous migration patterns in gel electrophoresis as reported. This was likely to be mainly due to proteolytic degradation and protein-protein crosslinking of Tamm-Horsfall protein and prothrombin. Protein profiles of calcium oxalate kidney stones were obtained by in-solution protease digestion followed by nanoLC-MALDI-tandem mass spectrometry, which resulted in identification of a total of 92 proteins in stones from 9 urolithiasis patients. Further analysis showed that protein species and their relative amounts were highly variable among individual stones. Although proteins such as prothrombin, osteopontin, calgranulin A and calgranulin B were found in most stones tested, some samples had high contents of prothrombin and osteopontin, while others had high contents of calgranulins. In addition, calgranulin-rich stones had various neutrophil-enriched proteins such as myeloperoxidase and lactotransferrin. These proteomic profiles of individual kidney stones suggest that multiple systems composed of different groups of proteins including leucocyte-derived ones are differently involved in pathogenesis of individual kidney stones depending on situations.

Increasing effect of an oral intake of L-hydroxyproline on the soluble collagen content of skin and collagen fragments in rat serum.

We examined the effects of oral L-hydroxyproline (Hyp) on collagen in the body. After 2 weeks' administration of Hyp (0.5 or 1 g/kg) to F344 male rats, the soluble collagen content of the skin had increased, and the serum concentration of collagen peptides was correlated with the skin content of soluble collagen. This result suggests that oral Hyp augmented collagen metabolism.