When the hydrophobic probe 1-anilino-8-naphthalenesulfonate (1.8 ANS) is bound to Hemorrhagin-1 (A

2

H-1) from A.Acutus venom

its excitation and emission maxima are at 370nm and 470nm respectively. There is a hydrophobic region in A

2

H-1.

K

d

=1.53×10

-5

M

n

=1.43. 1.8ANS does not inhibit hemorrhagic activity of A

2

H-1.Intensity of fluorescence emission of AaH-l-ANS is sensitive to the PH

EDTA

and temperature. The hemorrhagic activity of A

2

H-1 in these conditions shows corresponding changes.Energy transfer from Trp residus of A

2

H-1 to the bound ANS is observed. The efficency of energy transfer is 0.523. The Trp residus may be situated in hydrophobic region.Change of comformation of hydrophobic region of A

2

H-1 results in the change of hemorrhagic activity.