N hydroxysuccinimide sodium salt sulfo nhs

C-reactive protein (2.1 mg protein per ml (lowry)) from human plasma and anti-human C-reactive protein (anti-CRP, 54.7 mg protein per ml (Biuret)) antibody (produced in goat), anti-myoglobin (produced in rabbit, 1:500 protein dilution) as control antibody, myoglobin from human heart (≥95%, SDS-PAGE, 2 mg protein per ml (lowry)) as control antigen, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC, ≥99%) and N-hydroxysuccinimide sodium salt (sulfo-NHS, ≥98% (HPLC)) were purchased from Sigma Aldrich (Saint Louis MO). The stock CRP solution was stored at 4 ⁰C whereas the anti-CRP, anti-myoglobin and myoglobin solutions were stored at -20 °C. Highly pure de-ionized water (18.2 MΩcm) from super-Q Millipore system was used throughout the study. Phosphate buffered saline (PBS, 10 mM, pH 7.4) was prepared by dissolving PBS sachet (from Sigma Aldrich) in de-ionized water and was filtered using a 0.22 μm membrane filter before every use. Sodium hydroxide (NaOH, 1 mM) solution, for electrochemical etching, was prepared by dissolving appropriate quantity of NaOH pellets (from Sigma Aldrich) in de-ionized water. For continuous use, the anti-CRP solution was stored at 4 °C in working aliquots. Potassium hexacyanoferrate (III) for probe molecule (Fe[CN₆]^3-/4-) and all other regents used in the study were of analytic grade.