ALBERT

Beschreibung: The heat capacity, Cp, of synthetic hydroxyapatite [Ca5(PO4)3OH–OH-Ap], as well as of ten compositions along the OH-Ap-chlorapatite (Cl-Ap) join and 12 compositions along the OH-Ap-fluorapatite (F-Ap) join have been measured using relaxation calorimetry (heat capacity option of the Physical Properties Measurement System—PPMS) and differential scanning calorimetry (DSC) in the temperature range of 5–764 K. Apatites along the Cl-OH and F-OH joins were synthesized at 1100 °C and 300 MPa in an internally heated gas pressure vessel via an exchange process between synthetic fluorapatite or chlorapatite crystals (200–500 μm size) and a series of Ca(OH)2-H2O solutions with specific compositions and amounts relative to the starting apatite. The standard third-law entropy of OH-Ap, derived from the low-temperature heat capacity measurements, is S° = 386.3 ± 2.5 J mol−1 K−1, which is ~ 1% lower than that resulting from low-temperature adiabatic calorimetry data on OH-Ap from the 1950’s. The heat capacity of OH-Ap above 298.15 K shows a hump-shaped anomaly centred around 442 K. Based on published structural and calorimetric work, this feature is interpreted to result from a monoclinic to hexagonal phase transition. Super ambient Cp up to this transition can be represented by the polynomial: $$C_{p}^{{ext{OH - Ap}}} {}_{{298K - 442K}}left( {{ext{J mol}}^{ - 1} {ext{K}}^{- 1}} ight) = {1013.7-13735.5T^{{ - 0.5}}} + 2.616718,10^{7} T^{{ - 2}} - 3.551381,10^{9} T^{{ - 3}} .$$ C p OH - Ap 298 K - 442 K J mol - 1 K - 1 = 1013.7 - 13735.5 T - 0.5 + 2.616718 10 7 T - 2 - 3.551381 10 9 T - 3 . . The DSC data above this transition were combined with heat capacities computed using density functional theory and can be given by the Cp polynomial: $$C_{p}^{{ext{OH - Ap}}} {}_{{ 〉,442K}}left( {{ext{J mol}}^{ - 1} {ext{K}}^{- 1}} ight) = {877.2-11393.7 T^{ - 0.5}} + {5.452030,10^{7}} ,T^{- {2}} - {1.394125,10^{10}} ,T^{- {3}}$$ C p OH - Ap 〉 442 K J mol - 1 K - 1 = 877.2 - 11393.7 T - 0.5 + 5.452030 10 7 T - 2 - 1.394125 10 10 T - 3 . Positive excess heat capacities of mixing, ∆Cpex, in the order of 1–2 J mol−1 K−1, occur in both solid solutions at around 70 K. They are significant at these conditions exceeding the 2σ-uncertainty of the data. This positive ∆Cpex is compensated by a negative ∆Cpex of the same order at around 250 K in both binaries. At higher temperatures (up to 1200 K), ∆Cpex is zero within error for all solid solution members. As a consequence, the calorimetric entropies, Scal, show no deviation from ideal mixing behaviour within a 2σ-uncertainty for both joins. Excess entropies of mixing, ∆Sex, are thus zero for the OH-Ap–F-Ap, as well as for the OH-Ap–Cl-Ap join. The Cp–T behaviour of the OH-Ap endmember is discussed in relation to that of the F- and Cl-endmembers.

Beschreibung: Cryopreservation of cells is necessary for long periods of storage. However, some cell lines cannot be efficiently cryopreserved, even when optimized commercial cryoprotectants are employed. Previously, we found that a low-toxic synthetic zwitterion aqueous solution enabled good cryopreservation. However, this zwitterion solution could not cryopreserve some cells, such as human kidney BOSC cells, with good efficiency. Therefore, details of the cryoprotective effect of the zwitterions and optimization based on its mechanisms are required. Herein, we synthesized 18 zwitterion species and assessed the effects of the physical properties of water/zwitterion mixtures. Non-cell-permeable zwitterions can inhibit ice crystal formation extracellularly via direct interaction with water and intracellularly via dehydration of cells. However, cells that could not be cryopreserved by zwitterions were insufficiently dehydrated in the zwitterion solution. Dimethyl sulfoxide (DMSO) was combined as a cell-permeable cryoprotectant to compensate for the shortcomings of non-cell-permeable zwitterions. The water/zwitterion/DMSO (90/10/15, v/w/w) could cryopreserve different cells, for example freezing-vulnerable K562 and OVMANA cells; yielding ~1.8-fold cell viability compared to the case using a commercial cryoprotectant. Furthermore, molecular dynamics simulation indicated that the zwitterions protected the cell membrane from the collapse induced by DMSO.