4.4.1.16 - 4.4.1.16 hanging drop vapor diffusion method 4.4.1.16 purified enzyme in dimeric and tetrameric forms, sitting drop vapour diffusion method, 100 nl of 17 mg/ml protein solution with 100 nl of well solution 1 containing 100 mM HEPES, pH 6.7, and 10% PEG 6000, or well solution 2 containing 50 mM HEPES, pH 8.1, 200 mM ammonium nitrate and 25% PEG 3350, 20°C, 3 days or 7 days, respectively, X-ray diffraction structure determination and analysis of the two crystals forms at 2.1 A and 1.8 A resolution, respectively, modeling of dimeric enzyme complexed with pyridoxal 5'-phosphate