Plasma protein-binding ligands
The invention provides an isolated or purified peptide that binds at least one plasma protein. In one embodiment, the isolated or purified peptide binds to fibrinogen, comprises no more than 10 amino acids, and comprises an amino acid sequence Xaa 1 -Xaa 2 -Xaa 3 -Xaa 4 -Xaa 5 , and amino acid sequence Gly-Xaa 6 -Arg-Xaa 7 , or an amino acid sequence selected from specific amino acid sequences provided herein. Alternatively, the isolated or purified protein binds to α1 proteinase inhibitor and/or a protein complex comprising Apo-A1 lipoprotein and paraoxonase. The peptide comprises no more than 10 amino acids and comprises an amino acid sequence Xaa 8 -Xaa 1 -His-Xaa 1 -Xaa 3 , and amino acid sequence His-Xaa 8 -Xaa 9 -Xaa 1 -Xaa 10 -Xaa 2 , or an amino acid sequence selected from specific amino acid sequence provided herein. In addition, the invention provides isolated or purified peptide that binds to von Willebrand Factor. The peptide comprises an amino acid sequence Xaa 4 -Xaa 5 -Xaa 5 , an amino acid sequence Tyr-Leu-Xaa 11 -Xaa 4 -Xaa 12 -Thr, or an amino acid sequence selected from specific amino acid sequences provided herein.
1 . A method for specifically and selectively detecting and/or measuring the activity of paraoxonase in a fluid, which contains at least paraoxonase and phosphatases, said method comprising:
(a) contacting the fluid with a compound of formula I:
(b) measuring the fluorescence of a fluorescent product formed during the contacting; and
(c) correlating the measured fluorescence with the activity of paraoxonase, wherein R 3 is H, R 4 is methyl, R 5 is H, R 6 and R 8 are fluoro, R 9 and R 10 are ethyl and X 1 , X 2 and X 3 are O.
2 . The method of claim 1 , wherein the fluid is a biological fluid or an environmental fluid.
3 . The method of claim 2 , wherein the biological fluid is selected from the group consisting of blood, blood-derived compositions, serum, cerebrospinal fluid, urine, saliva, milk, ductal fluid, tears, semen, cell or tissue extracts, culture medium from the expression of paraoxonase or mutations of paraoxonase and samples arising from the fractionation of paraoxonase or HDL from biological samples.
4 . The method of claim 3 , wherein the cell or tissue extract is of brain, artery, vein or gland.
5 . The method of claim 2 , wherein the fluid is an environmental fluid.
6 . The method of claim 5 , wherein the environmental fluid is an extract of soil, water or swab.
7 . A method for selectively detecting paraoxonase in a sample suspected to contain a paraoxonase and a phosphatase comprising:
(a) contacting the sample with a compound of formula I:
wherein
R 3 is H;
R 4 is methyl;
R 5 is H;
R 6 and R 8 are halo;
R 9 and R 10 are ethyl; and
X 1 , X 2 , and X 3 are independently O;
(b) measuring the fluorescence of a fluorescent product formed during the contacting; and
(c) correlating the measured fluorescence with the activity of paraoxonase.
8 . A method for specifically and selectively detecting and/or measuring the activity of paraoxonase immobilized on a support, said method comprising:
(a) contacting the support with a compound of formula I:
wherein
R 3 is H;
R 4 is methyl;
R 5 is H;
R 6 and R 8 are halo;
R 9 and R 10 are ethyl; and
X 1 , X 2 , and X 3 are independently O;
(b) measuring the fluorescence of a fluorescent product formed during the contacting; and
(c) correlating the measured fluorescence with the activity of the paraoxonase enzyme.
9 . The method of claim 8 , wherein the support is a membrane, resin, biosensor, microtiter plate, nanotube or dipstick.