We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was observed in real-time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event. We interpret the light-curve "fine structure" as indicating transit of the lens across the extended face of the source star. This signifies resolution of a star several kpc distant.We find a lens angular impact parameter θ min /θ source = 0.715 ± 0.003. This information, along with the radius and distance of the source, provides an additional constraint on the lensing system. Spectroscopic and photometric data indicate the source is an M4 III star of radius 61 ± 12R ⊙ , located on the far side of the bulge at ∼ 9 kpc. We derive a lens angular velocity, relative to the source, of 21.5 ± 4.9 km s −1 kpc −1 , where the error is dominated by uncertainty in the source radius. Likelihood analysis yields a median lens mass of 0.67 +2.53 −0.46 M ⊙ , located with 80% probability in the Galactic bulge at a distance of 6.93 +1.56 −2.25 kpc. If the lens is a main-sequence star, we can include constraints on the lens luminosity. This modifies our estimates to M lens = 0.53 +0.52 −0.35 M ⊙ and D lens = 6.57 +0.99 −2.25 kpc. Spectra taken during the event show that the absorption line equivalent widths of Hα and the TiO bands near 6700Å vary, as predicted for microlensing of an extended source. This is most likely due to center-to-limb variation in the stellar spectral lines. The observed spectral changes further support our microlensing interpretation. These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly.Subject headings: dark matter -gravitational lensing -stars: low-mass, brown dwarfsstars: late-type -stars: atmospheres Table 4. Photometry of the source star in MACHO 95-30Observed Extinction Dereddened Abs Mag, 8 kpc Abs Mag, 9 kpc V = 16.21 A V = 1.35 V 0 = 14.86 M V = +0.34 M V = +0.59 K = 9.98 A K = 0.15 K 0 = 9.83 M K = −4.69 M K = −4.45 V − R = 1.39 E(V − R) = 0.34 V − R 0 = 1.05 J − K = 1.12 E(J − K) = 0.23 J − K 0 = 0.89 H − K = 0.26 E(H − K) = 0.08 H − K 0 = 0.18 V − K = 6.23 E(V − K) = 1.21 V − K 0 = 5.03 Bolometric BC K = −2.7 ± 0.1 M bol = −2.0 M bol = −2.25

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Steroid monooxygenase of Rhodococcus rhodochrous is a Baeyer-Villigerase catalyzing the insertion of an oxygen atom between the C(17)- and C(20)-carbons of progesterone to produce testosterone acetate. The 5.1-kbp-long BamHI DNA fragment containing the steroid monooxygenase gene, smo, was cloned from the chromosomal DNA and sequenced. The smo gene is 1,650 nucleotides long, starts with a TTG codon, and ends with a TGA codon. The deduced amino acid sequence indicates that the enzyme protein consist of 549 amino acid residues with a molecular mass of 60,133. Thus, the molecular mass of the holoenzyme is 60,919. The amino acid sequence is highly homologous (41.2% identity) to that of cyclohexanone monooxygenase of Acinetobacter sp. In the upstream of the smo gene, the genes of heat shock proteins, dnaK, grpE, and dnaJ, located on the complementary strand, and the DNA-inserts of pSMO and pD1, which contains the ksdD gene, were joined at the BamHI site of the dnaJ gene. The smo gene was modified at the initiation codon to ATG and ligated with an expression vector to construct a plasmid, pSMO-EX, and introduced into Escherichia coli cells. The transformed cells hyperexpressed the steroid monooxygenase as an active and soluble protein at more than 40 times the level in R. rhodochrous cells. Purification of the recombinant monooxygenase from the E. coli cells by simplified procedures yielded about 2.3 mg of enzyme protein/g wet cells. The purified recombinant steroid monooxygenase exhibited indistinguishable molecular and catalytic properties from those of the R. rhodochrous enzyme.

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