Summary Platelets play a central role in thrombosis, hemostasis, and inflammation. We show that activated platelets release inorganic polyphosphate (polyP), a polymer of 60-100 phosphate residues that directly bound to and activated the plasma protease factor XII. PolyP-driven factor XII-activation triggered release of the inflammatory mediator bradykinin by plasma kallikrein-mediated kininogen processing. PolyP increased vascular permeability and induced fluid extravasation in skin microvessels of mice. Mice deficient in factor XII or bradykinin receptors were resistant to polyP-induced leakage. PolyP initiated clotting of plasma via the contact pathway. Ablation of intrinsic coagulation pathway proteases factor XII and factor XI protected mice from polyP-triggered lethal pulmonary embolism. Targeting polyP with phosphatases interfered with procoagulant activity of activated platelets and blocked platelet-induced thrombosis in mice. Infusion of polyP restored defective plasma clotting of Hermansky-Pudlak Syndrome patients, which lack platelet polyP. The data identify polyP as a new class of mediator having fundamental roles in platelet-driven proinflammatory and procoagulant disorders.

Donor molecules undergo dramatic changes in their chemical properties on coordination to a transit&-metal atom. Highly reactive species can be trapped and studied as ligands. Conversely, stable compounds can be activated to undergo novel reactions. Sulfur dioxide complexes have generally been studied from a structural viewpoint, their reactivity having been somewhat neglected. The unstable sulfur oxides SO, S20, and S202 are still often regarded as laboratory curiosities. Their successful stabilization in transition-metal complexes has now made them accessible to detailed study, in the course of which many relationships to the chemistry of SO2 complexes have become apparent.

A convenient, high-yield (91%) synthesis of [(η5-C5Me5)Ru(NCMe)3]PF6 (4−PF6) by zinc reduction of [(η5-C5Me5)RuCl2] n (1) in acetonitrile solution is described. Two acetonitrile ligands of 4−PF6 are readily exchanged for either PMe3 or the chelating diphosphines bis(dimethylphosphino)methane, (2S,3S)-bis(diphenylphosphino)butane, or (2S,4S)-bis(diphenylphosphino)pentane. The remaining nitrile ligand is still labile, allowing easy access to a number of substitution products [(η5-C5Me5)Ru(PR3)2(L)].

Electrotransfection and electrofusion, both widely used in research and medical applications, still have to face a range of problems, including the existence of electroporation-resistant cell types, cell mortality and also great batch-to-batch variations of the transfection and fusion yields. In the present study, a systematic analysis of the parameters critical for the efficiency and robustness of electromanipulation protocols was performed on five mammalian cell types. Factors examined included the sugar composition of hypotonic pulse media (trehalose, sorbitol or inositol), the kinetics of cell volume changes prior to electropulsing, as well as the growth medium additives used for post-pulse cell cultivation. Whereas the disaccharide trehalose generally allowed regulatory volume decrease (RVD), the monomeric sugar alcohols sorbitol and inositol inhibited RVD or even induced secondary swelling. The different volume responses could be explained by the sugar selectivity of volume-sensitive channels (VSC) in the plasma membrane of all tested cell types. Based on the volumetric data, highest transfection and fusion yields were mostly achieved when the target cells were exposed to hypotonicity for about 2 min prior to electropulsing. Longer hypotonic treatment (10-20 min) decreased the yields of viable transfected and hybrid cells due to (1) the cell size reduction upon RVD (trehalose) or (2) the excessive losses of cytosolic electrolytes through VSC (inositol/sorbitol). Doping the plasma membrane with lipophilic anions prevented both cell shrinkage and ion losses (probably due to VSC inhibition), which in turn resulted in increased transfection and fusion efficiencies.

The sulfur oxides SO, SO₂ and SO₃, and thioformaldehyde H₂C=S and its oxides H₂C=SO and H₂C=SO₂ form stable coordination compounds with a range of transition metals. The complexes have a rich chemistry which differs markedly from that of the free ligands. Typical reactions involve electrophilic additions, nucleophilic additions and cycloadditions. The complexes can be used as synthons to incorporate these small molecules as building blocks into larger structures.

l3C NMR data and CO stretching force constants of 23 anionic and neutral tungsten pentacarbonyl complexes, W(CO)sL, are compiled. Changes of the 13C chemical shift of the carbonyl groups are shown to arise mainly from the [2M + ß* (? ß] term of the paramagnetic shift contribution. The correlation between 5(I3C) and &(CO) is good even if the ligands L span a wide range in terms of donor/acceptor properties. Strong, single-faced -acceptor ligands L, however, give rise to an additional downfield shift of the 13C resonance of the CO group trans to L. This is explained as being a result of the breakdown of the cylindrical symmetry of the -bonding system within the L-W-C-0 fragment. On the basis of V(183W-13C) of the carbonyl group trans to L, the following trans-influence series of ligands L toward tungsten(O) is established: Ph2C > CO > olefins > CN-, P(OR)3, PR3 > H", CHf, NCS", 0C(0)R", py > RNH2, RCN, SC(S)R", AsR3 > SbR3, SH" > Cl" > Br" > I". A comparison between this trans-influence series and those for square-planar Rh(I) and Pt(II) complexes reveals the importance of metal-carbon bonding in octahedral tungsten carbonyl complexes as a mechanism to strengthen the interaction.

The direct molybdenum-catalyzed sulfuration of a variety of isonitriles with elemental sulfur or propene sulfide as sulfur donors affords the corresponding isothiocyanates in good yields and under mild reaction conditions. A catalytic cycle is suggested, in which the molybdenum oxo disulfur complex operates as the active sulfur-transferring species. A novel adduct between the isonitrile and the molybdenum complex has been characterized by X-ray analysis and its association constant determined by UV-vis spectroscopy, but this adduct appears not to be involved in the sulfur-transfer process.

The molybdenum oxo complexes 1a and 1b catalyze efficiently the sulfur transfer to a series of alkenes 4 and allenes 6, for which elemental sulfur, phenylthiirane, or methylthiirane have been employed as sulfur sources to afford the corresponding episulfides 5 and 7. The most effective catalytic episulfidation system to date is the combination of the dithiophosphate-ligated oxo complex 1b and phenylthiirane (Ibeta). This metathesis process is efficient enough to convert usually reluctant alkenes (cyclopentene, cycloheptene, Z-cyclooctene, Z-cyclononene, E-cyclodecene, norbornene, and even bicyclopropylidene) to their episulfides in good yields under mild conditions. The direct catalytic sulfuration of allenes (cyclonona-1,2-diene, cyclonona-1,2,5-triene, cyclodeca-1,2-diene, and 2,4-dimethylpenta-2,3-diene) to their labile methylenethiiranes is unprecedented.