Mediator

A composition comprising:

• an enzyme;
• and
• an electrode modifying agent or an electron transfer promoting agent comprising a compound having a property of being adsorbed, without being bound to a polymer or without being polymerized, onto an electrode untreated with an acid,
• wherein the compound is a compound having a structure of formula I or formula II:
• wherein
• R1 is —NR7R8, —N═N—R9, or —N+≡N,
• R2 is —NR10R11 or —N═N—R12,
• R7 and R8 are each independently hydrogen, or linear or branched C1-7 alkyl, C1-7 alkenyl, C1-7 alkynyl, C3-9 cycloalkyl, phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, phenanthrenyl, acetyl, carboxy, furanylformyl, pyrazolylformyl, 1-methyl-1H-pyrazol-5-ylformyl, 9,9-dimethylfluoren-2-yl, —N+≡N, —N═N-phenyl, benzyl,
• which may optionally be substituted with one or more X or V,
• R10 is hydrogen, or linear or branched C1-7 alkyl, C1-7 alkenyl, C1-7 alkynyl, C3-9 cycloalkyl, phenyl, 1-naphthyl, 2-naphthyl, anthracenyl or phenanthrenyl, which may optionally be substituted with one or more X or V,
• R3, R4, R5 and Re are each independently hydrogen, or linear or branched C1-7 alkyl, C1-7 alkenyl, C1-7 alkynyl, C1-7 alkoxy, halo, nitro, cyano, carboxy, sulfo, hydroxy or amino, which may optionally be substituted with one or more Y,
• or R3 and R4, or R5 and Re, together with the benzene ring containing these moieties, form a benzene ring, or
• which may optionally be substituted with one or more oxo, X or W,
• wherein * is bonded to the carbon atom bonded to R3, and ** is bonded to the carbon atom bonded to R4, or * is bonded to the carbon atom bonded to R5, and ** is bonded to the carbon atom bonded to R6,
• R11 is selected from the group consisting of phenyl, 1-naphthyl, 2-naphthyl, anthracenyl and phenanthrenyl, which may optionally be substituted with one or more X or Z,
• R9 is selected from the group consisting of hydrogen, and phenyl, 1-naphthyl, 2-naphthyl, anthracenyl and phenanthrenyl, which may optionally be substituted with one or more X,
• R12 is selected from the group consisting of phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, phenanthrenyl, and
• which may optionally be substituted with one or more X, W, isothiocyanate, or halosulfonyl,
• wherein
• V is —O-acryloyl, acetylamino, or phenyl, which may optionally be substituted with C1-7 alkyl, W is D- or L-alanylsulfonyl, D- or L-valylsulfonyl, D- or L-leucylsulfonyl, D- or L-methionylsulfonyl, D- or L-prolylsulfonyl, D- or L-tryptophylsulfonyl, D- or L-glycylsulfonyl, D- or L-cysteinylsulfonyl, D- or L-isoleucylsulfonyl, D- or L-phenylalanylsulfonyl, D- or L-tyrosylsulfonyl, D- or L-serylsulfonyl, D- or L-threonylsulfonyl, D- or L-asparaginylsulfonyl, D- or L-glutamylsulfonyl, D- or L-arginylsulfonyl, D- or L-histidylsulfonyl, D- or L-lysylsulfonyl, D- or L-asparagylsulfonyl, D- or L-glutaminylsulfonyl, -C(═O)—O-succinimidyl, acetyl, trifluoroacetyl, benzoylamino, —N═N-phenyl, phenylamino, or diaminophenylazophenyl, which may optionally be substituted with one or more amino, C1-7 alkyl, or aminoalkyl, or phenylazo, which may optionally be substituted with one or more X, naphthylazo, which may optionally be substituted with one or more Y, acetylamino,
• X is linear or branched C1-7 alkyl, C1-7 alkenyl, C1-7 alkynyl, C1-7 alkoxy, halo, hydroxy, nitro, carboxy, cyano, sulfo, amino or alkylamino, which may optionally be substituted with one or more substituents selected from the group consisting of halo, amino, cyano, carboxy, carbonyl, alkoxy, alkylamino, nitroso, nitro and sulfo,
• Y is selected from the group consisting of halo, amino, cyano, carboxy, carbonyl, hydroxy, alkoxy and sulfo, and
• Z is —SO2—CH═CH2, —SO2—C2H4—O—SO3H, or 4,6-dichlorotriazin-2-ylamino,
• or a salt, an anhydride or a solvate thereof,
• wherein the compound is neither N-methyl-N-phenyl-1,4-phenylenediamine nor N-methyl-N-(3-methoxyphenyl)-1,4-phenylenediamine, and
• wherein the compound is neither