Toward the development of new photolabile protecting groups that can rapidly release bioactive compounds upon photolysis with visible light

The synthesis and characterization of a new photolabile protecting group (caging group) for carboxylic acids, the 2-(dimethylamino)-5-nitrophenyl (DANP) group, is described. This compound has a major absorption band in the visible wavelength region with a maximum near 400 nm (epsilon400 = 9077 M(-1) cm(-1) at pH 7.4 and 21 degrees C). The caging group is attached through an ester linkage to the carboxyl functionality of beta-alanine, which activates the inhibitory glycine receptor in the mammalian central nervous system. Such caged compounds play an important role in transient kinetic investigations of fast cellular processes. Upon photolysis of DANP-caged beta-alanine, the caging group is released within 5 micros. Quantum yields of 0.03 and 0.002 were obtained in the UV region (308 and 360 nm) and the visible region (450 nm), respectively. Laser-pulse photolysis experiments, using 337 or 360 nm light, were performed with the caged compound equilibrated with HEK 293 cells transiently transfected with cDNA encoding the alpha1 homomeric, wild-type glycine receptor. The experiments demonstrated that neither DANP-caged beta-alanine nor its byproducts inhibit or activate the glycine receptors on the cell surface. Under physiological conditions, the DANP-caged beta-alanine is water-soluble and stable and can be used for transient kinetic measurements.     

Vibrational spectroscopy of solids under high pressures. Part I. Raman spectra of inorganic hexafluorometallate compounds

Raman spectra of a series of isomorphous hexafluorometallates (TlSbF₆; BaMF₆, M = Si, Ge, Sn, and Ti, space group $\text{R}\text{3}\text{m-D}{}^5{}_{\mathrm{3d}}\text{, Z = 1}$) have been measured under high pressures up to 25 kbar with a new opposed sapphire anvil cell. Pressure calibration has been achieved by means of the R₁ fluorescence band of ruby. The frequency of the only Raman active lattice mode (libration of the octahedral anion) of each compound shows a higher pressure dependence than do the internal vibrations of the anions. The E_g components of the ν₅ modes of the MF₆ octahedra which are coupled to the E_g lattice modes because of their same symmetries and small frequency differences exhibit higher pressure sensitivities than do the uncoupled internal modes. These findings may be used as a further means for symmetry assignment. BaGeF₆ undergoes a reversible phase transition at 9.6 kbar; the split librational modes of the high-pressure phase show the highest pressure dependences of up to about 3 cm^?1 · kbar^?1 found in this investigation.     

K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

The structure of dipotassium μ₃‐oxido‐tris[sulfitomercurate(II)], K₂[O(HgSO₃)₃], is characterized by segregation of the K⁺ cations and complex [O(HgSO₃)₃]²⁻ anions into layers parallel to (010). The anion has m symmetry and is a new example of a μ₃‐oxido‐trimercurate complex with a central [OHg₃] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O—Hg = 2.072 Å and mean Hg—O—Hg = 110.8°). The two independent Hg—S bonds have nearly the same length (mean Hg—S = 2.335 Å). Due to intermolecular O...Hg donor–acceptor interactions greater than 2.65 Å, the O—Hg—S fragments are slightly bent. The [KO₉] coordination polyhedron of the K⁺ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination.     

Structural Studies of New Sulfito Mercurates(II) with General Formula xM[XHgSO3]middot;yHgX2·zMX·nH2O (M = NH4, K; X = Cl,Br)

Several solid phases with the general formula xM[XHgSO₃]·yHgX₂·zMX·nH₂O were obtained from aqueous solutions during phase formation studies in the systems M₂SO₃/HgX₂ (M = NH₄, K; X = Cl, Br). All phases were structurally characterized on the basis of single crystal X‐ray diffraction data and adopt new structure types. Compounds with x, y, z = 1 and n = 0 are isostructural (structure type I ) and crystallise with two formula units in space group P2₁/m and lattice parameters of a ≈ 9.7, b ≈ 6.2, c ≈ 10.4Å, β ≈ 111°. Compounds with x, y = 1 and z, n = 0 (structure type II ) crystallize in space group Cmc2₁ with four formula units and lattice parameters of a ≈ 5.9, b ≈ 22.0, c ≈ 6.9Å. The structures with x = 2, y, z = 1 and n = 0 are likewise isostructural (stucture type III ) and consist of four formula units in space group Pnma with lattice parameters of a ≈ 22.2, b ≈ 6.1, c ≈ 12.4Å. K[HgSO₃Cl]·KCl·H₂O is the only representative where x = 1, y = 0, z = 1 and n = 1 (structure type IV ). It is triclinic (space group ) with four formula units and lattice parameters of a = 6.1571(8), b = 7.1342(9), c = 10.6491(14) Å, α = 76.889(2), β = 88.364(2), γ = 69.758(2)°. Characteristic for all structures types is the segregation of the M⁺ cations and the anions and/or HgX₂ molecules into layers. The [XHgSO₃]⁻ anions are present in all structures and have m symmetry, except for K[HgSO₃Cl]·KCl·H₂O with 1 symmetry (but very close to m symmetry). The different [XHgSO₃] units exhibit very similar Hg‐S distances (average 2.372Å) and are more or less bent with ∠(X‐Hg‐S) angles ranging from 159.7 to 173.7°. The molecular HgX₂ entities present in structure types I ‐ III deviate only slightly from linearity with ∠(X‐Hg‐X) angles ranging from 174 to 179°. The structures are stabilised by interaction of the K⁺ or NH₄⁺ cations that are located between the anionic layers or in the vacancies of the framework, by K‐O contacts or, in case of ammonium compounds, by medium to weak hydrogen bonding interactions of the type N‐H···O.