title: Indocyanine green as a noncovalent, pseudofluorogenic label for protein determination by capillary electrophoresis.
abstract: Indocyanine green (ICG)--a negatively charged, polymethine dye--can interact noncovalently with proteins to form fluorescent complexes, with excitation and emission maxima near 780 and 820 nm, respectively. This behavior was realized utilizing either a 100 mM phosphate buffer or a 25 mM citric acid buffer, both at pH 3.1. The behavior of ICG under these conditions, termed pseudofluorogenic, rendered the dye suitable for use as a label for protein determination in capillary electrophoresis with diode laser-induced fluorescence detection (CE-LIF). To this end, pseudofluorogenic ICG was used both as an on-column label for human serum albumin (HSA) and as a precolumn label for a model mixture of proteins, including ribonuclease A, transferrin, and cytochrome c. These ICG-labeled proteins were successfully resolved in less than 11 min, with no interference from excess, unbound dye.
authors.affiliation: Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: McCorquodale
authors.forename: C L
authors.initials: CL
authors.lastname: Colyer
mesh_terms: D000818:Animals; D002021:Buffers; D019343:Citric Acid; D003574:Cytochrome c Group / Q000032:analysis / Q000302:isolation & purification; D019075:Electrophoresis, Capillary / Q000379:methods*; D005456:Fluorescent Dyes / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D007208:Indocyanine Green / Q000032:analysis* / Q000737:chemistry; D015394:Molecular Structure; D010710:Phosphates; D011506:Proteins / Q000032:analysis* / Q000302:isolation & purification; D012259:Ribonuclease, Pancreatic / Q000032:analysis / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000032:analysis; D013050:Spectrometry, Fluorescence; D014168:Transferrin / Q000032:analysis / Q000302:isolation & purification
chemical_list: D002021:Buffers; D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D010710:Phosphates; D011506:Proteins; D012709:Serum Albumin; D014168:Transferrin; D019343:Citric Acid; D012259:Ribonuclease, Pancreatic; D007208:Indocyanine Green