Arkray, Inc.

Norio Inamura

Satoshi Yonehara

The present invention provides a stabilizer that can stabilize a salt of 10-(carboxymethylaminocarbonyl)-3,7-bis(dimethylamino)phenothiazine or a derivative thereof even under the existence of moisture or under light irradiation. A compound described in at least one of (1) and (2) below is used as the stabilizer of the salt of 10-(carboxymethylaminocarbonyl)-3,7-bis(dimethylamino)phenothiazine or the derivative thereof. 

Stabilizer of color former and use thereof

The present invention provides a phenothiazine-derivative color-measuring method that can detect a phenothiazine-derivative color even at a wavelength longer than the wavelength that exhibits maximum absorption. A phenothiazine-derivative color is detected, by adding a 5-hydroxy-1-(4-sulfophenyl)-4-(4-sulfophenylazo)pyrazole-3-carboxylic acid salt, 6-hydroxy-5-(4-sulfophenylazo)-2-naphthalenesulfonic acid salt, 3-hydroxy-4-(4-sulfonaphthylazo)-2,7-naphthalenedisulfonic acid salt, 7-hydroxy-8-(4-sulfonaphthylazo)-1,3-naphthalenedisulfonic acid salt, 3',6&#x2032;-dihydroxy-2&#x2032;,4&#x2032;,5&#x2032;,7&#x2032;-tetraiodospiro[isobenzofuran-1(3H),9&#x2032;-(9H)xanthene]-3-one salt, 3&#x2032;,6&#x2032;-dihydroxy-2&#x2032;,4&#x2032;,5&#x2032;,7&#x2032;-tetrabromo-4,5,6,7,-tetrachlorospiro[isobenzofuran-1(3H),9&#x2032;-[9H]xanthene]-3-one salt, 4,5,6,7-tetrachloro-3&#x2032;,6&#x2032;-dihydroxy-2&#x2032;,4&#x2032;,5&#x2032;,7&#x2032;-tetraiodospiro[isobenzofuran-1(3H),9&#x2032;-[9H]xanthene]-3-one salt or flavonoid-based color to the reaction system containing a phenothiazine-derivative color, and then measuring the light absorbance at a wavelength of 610 to 730 nm.

Method for detecting phenothiazine-derivative color and color-developer reagent used therein

A method of measuring HbA1c is provided that, even with a whole blood sample after storage, measurement accuracy substantially equal to a whole blood sample right after collection can be maintained. Whole blood is stored in a presence of a glycolytic inhibitor and protease is added to the stored whole blood sample to cleave hemoglobin in the whole blood sample. Then a glycated part of a hemoglobin fragment thereby obtained is treated with fructosyl amine oxidase. Thereafter, a glycation degree of HbA1c is determined by measuring a redox reaction between the glycated part and the fructosyl amine oxidase. Further, instead of storage of the whole blood in a presence of the glycolytic inhibitor, a strong electrolyte substance such as KCl, KSO, KNO, NaCl, NaSO, NaNO, MgCl, MgSO, Mg(NO), etc. is added to the whole blood after storage and a protease treatment is performed in a presence of the strong electrolyte substance. According to these methods, fluctuation in a measurement value of HbA1c due to storage of the whole blood can be avoided.

Method of measuring HbA1c

A liquid reagent in which a methylene blue compound color former is stably stored in a liquid state; and a method of stabilizing a methylene blue compound color former in a liquid state. A methylene blue compound color former is stabilized by causing it to coexist with either a quaternary ammonium compound having a Cor higher hydrocarbon chain or a salt thereof in a liquid medium. Examples of the methylene blue compound color former include 10-(carboxymethylaminocarbonyl)-3,7-bis(dimethylamino) phenothiazine.

Liquid reagent of color former and method of stabilizing the same

The present invention provides a method for cleaving a glycated protein to obtain an amino acid or a peptide efficiently with a protease. By treating the glycated protein with the protease in the presence of a compound represented by R&#x2014;X, the amino acid or the peptide is obtained by the cleavage. The R represents an alkyl compound with a carbon number of 9 or more, and preferably is straight-chain alkyl or straight-chain acyl with a carbon number of 9 to 16, branched-chain alkyl or branched-chain acyl with a carbon number of 10 to 40 and a main-chain carbon number of 9 to 16, or straight-chain alkyl that is substituted by cycloalkyl (a carbon number of the cycloalkyl ranges from 3 to 8, and a carbon number of the straight chain ranges from 4 to 13), where X is a sugar residue. Moreover, the glycated protein is, for example, glycated hemoglobin, and preferably &#x3b2;-chain N-terminal amino acid or a &#x3b2;-chain N-terminal peptide is cleaved by the protease treatment.

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Kyoto, Japan

Norio Inamura