Phase structures and transitions in fully hydrated diacyltrehalose

Real-time X-ray diffraction study at different scan rates of phase transitions for dipalmitoylphosphatidylcholine in KSCN

Multibilayer arrays of dipalmitoylphosphatidylcholine (DPPC) in 1 M KSCN were characterized using real-time X-ray diffraction and differential scanning calorimetry. A phase transition sequence was observed as a function of increasing temperature which involved changes from the interdigitated subgel (Lc(inter)) to interdigitated gel (L beta(inter)) to disordered (L alpha) bilayer states. The phase transition mechanisms were unambiguously determined by comparison of results from fast and slow scans. The Lc(inter)-->L beta(inter) phase transition was shown to involve a continuous change in acyl chain spacing between the rectangular subgel acyl chain unit cell into an hexagonal gel acyl chain unit cell. The mechanism is similar to that for subgel to gel state transitions involving non-interdigitated DPPC bilayers.

Phases and phase transitions of the glycoglycerolipids

LIPIDAT is a computerized database providing access to the wealth of information scattered throughout the literature concerning synthetic and biologically derived polar lipid polymorphic and mesomorphic phase behavior. The database is considered comprehensive for glycerophospholipids, glycoglycerolipids, sphingolipids and natural membrane extracts. Here, a review of the LIPIDAT data subset referring to glycoglycerolipids is presented together with an analysis of these data. The glycoglycerolipids subset represents 4% of all LIPIDAT records. It includes data collected over a 20-year period and consists of 419 records obtained from 37 articles in 13 journals. An analysis of the data in the subset has allowed us to identify trends in hydrated glycoglycerolipids phase behavior reflecting differences in hydrocarbon chain length, chain branching, chain-glycerol linkage type (ether vs. ester), sugar headgroup-glycerol linkage type (alpha vs. beta) and sugar headgroup identity. Included is a summary of the data concerning the effect of pH and of stereochemical purity on glycoglycerolipid phase behavior. Information on the mesomorphism of biologically derived and dry glycoglycerolipids is also presented. This review includes 92 references.