No abstract

Mineralization is the most fundamental process in vertebrates. It is predominantly mediated by osteoblasts, which secrete mineral precursors, most likely through matrix vesicles (MVs). These vesicular structures are calcium and phosphate rich and contain organic material such as acidic proteins. However, it remains largely unknown how intracellular MVs are transported and secreted. Here, we use scanning electron-assisted dielectric microscopy and super-resolution microscopy for assessing live osteoblasts in mineralizing conditions at a nanolevel resolution. We found that the calcium-containing vesicles were multivesicular bodies containing MVs. They were transported via lysosome and secreted by exocytosis. Thus, we present proof that the lysosome transports amorphous calcium phosphate within mineralizing osteoblasts.

No abstract

Reaction of Rh(I) -hydride complexes RhH(P(z'-Pr)3)3, RhH(N2)(PPh(r-611)2)2, and Rh2H2(q-N2)(P(c-C6Hl ,)3)4 with CO? in the presence of H?0 has been found to afford novel dihydrido bicarbonato complexes RhH2(0?C0H)L2 (1, L = P(/-Pr)3; 2, L = PPh(r-Bu)2; 3, L = P(c-C6H 11)3). The crystal and molecular structure of 1 has been determined at -160 °C.The complex RhH2(0?COH)(P(/-Pr)3)2 (1) crystallizes in the monoclinic space group C\h-P2\/c, with four formula units in a cell of dimensions a = 15.82 (I) Á, b = 10.88 (1) A, c = I 5.49 (1) Á, ß = 1 14.5 (1)°, V = 2428 Á3. In the solid state 1 consists of distorted octahedral Rh(III) centers coupled by intermolecular hydrogen bonding between bicarbonato ligands. These dihydrido bicarbonato complexes, and analogous dihydrido formato complexes, reduce C02 to form Rh(l) carbonyl bicarbonato and formato complexes and H20. 1587 s b 1338 s 792 m RhH2(02C0H)[PPh(z-Bu)2]2 (2) 2145 m,2220 m 2660 m 1583 s b 1340 s 802 m RhH2(02C0H)[P(c-C6HM)3]2(3)2138 m, 2158 m( (2110, 2160) 2640 m 1585 s 1410 w 1340 s 790 m Rh(C0)(02C0H)[P(c-C6Hn)3]2(6) 1942 s 2650 w 1608 s 1420 s 1355 s 821 m Rh(C0)(02C0D)[P(c-C6Hn)3]2 1942 s 2087 w 1590 s 1062 s 1405 s 821 m Rh(13CO)(G2'3COH)[P(c-C6H,,),]2 1900 s 2657 w 1575 s 1402 w 1345 s 822 m Rh(CO)(02COH)[P(Z-Pr)3]2 (7) 1952 s 2600 w 1615 s 1413 s 1350 s 823 m Rh(C0)(02C0H)(PPh3), 1968 s 2650 w 1600 s 1430 sd 1350 s 819 m (OsCOH)22" <• 2620 w 1618 s 1405 s 1367 s 830 m (OsCOD)22" f 2055 w 1615 s 1050 s 1392 s 830 m "stretching; 5, in-plane bending; tt, out-of-plane bending. * The band probably overlaps with that of Nujol. ' Sample recrystallized from toluene. The value in parentheses is for the sample recrystallized from THF. d The band is a composite of 50ho and Pp-ph. *' Reference 46.

No abstract

The shapes of giant unilamellar vesicles (GUVs) enclosing polymer molecules at relatively high concentration, used as a model cytoplasm, significantly differ from those containing only small molecules. Here, we investigated the effects of the molecular weights and concentrations of polymers such as polyethylene glycol (PEG), bovine serum albumin (BSA), and DNA on the morphology of GUVs deflated by osmotic pressure. Although small PEG (MW < 1000) does not alter the mode of shape transformation even at >10% (w/w), PEG with MW > 6000 induces budding and pearling transformation at above 1% (w/w). Larger PEG frequently induced small buddings and tubulation from the membrane of mother GUVs. A similar trend was observed with BSA, indicating that the effect is irrelevant to the chemical nature of polymers. More surprisingly, long strands of DNA (>10 bp) enclosed in GUVs induced budding transformation at concentrations as low as 0.01-0.1% (w/w). We expect that this molecular size dependency arises mainly from the depletion volume effect. Our results showed that curving, budding, and tubulation of lipid membranes, which are ubiquitous in living cells, can result from simple cell-mimics consisting of the membrane and cytosolic macromolecules, but without specific shape-determining proteins.

No abstract

Micelle formation in water and adsorbed film formation at the air/water interface were investigated by surface tension measurement of a mixed surfactant system: the combination of sodium salt of R-sulfonatomyristic acid methyl ester (R-SMy‚Me) with decanoyl-N-methylglucamide (MEGA-10). R-SMy‚ Me and MEGA-10 can form well-mixed micelles with the aid of a strong interaction between headgroups, and accordingly the critical micelle concentration (cmc) as a function of mole fraction of MEGA-10 in the surfactant mixture (XMEGA10) deviates negatively from ideal mixing. The micellar phase curve (cmc-YMEGA10 relation) was simulated by using the interaction parameter ωR ) -2.1; the curve indicated the existence of an azeotrope formed by a 3:2 mixture (at XMEGA10 ) YMEGA10 ) 0.4). Further, we derived equations related to the composition in the adsorbed film (Zi) equilibrated with monomers in bulk solution and to the interaction parameter (WA), and then constructed a phase diagram including two relations of cmc vs XMEGA10 and cmc vs ZMEGA10. From the diagram an azeotrope was found to be formed by the 1:1 mixture (at XMEGA10 ) ZMEGA10 ) 0.5), suggesting that the composition in micelles (Yi) differs from that in the adsorbed film (Zi). The surface tension (γ) vs logarithmic molality (ln m) curve at every 0.1 increment in XMEGA10 showed synergistically enhanced surface activity. From the slope of the γ vs ln m curve just below cmc, the surface excess (Γ) was determined and then the mean molecular area (Am) was calculated as a function of XMEGA10. By analysis of Am data, the partial molecular area (PMA) of each component was determined as a function of XMEGA10; this also showed a large deviation from ideal mixing (the additivity rule).