scholarly journals Phase Transitions and Conformational Changes in Monolayers of Human Apolipoproteins CI and AII

2003 ◽  
Vol 107 (46) ◽  
pp. 12897-12897
Author(s):  
Jaime Ruiz-García ◽  
Abel Moreno ◽  
Gerald Brezesinski ◽  
Helmuth Möhwald ◽  
Jaime Mas-Oliva ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Conformational Changes

A combined approach to characterize ligand-induced solid–solid phase transitions in biomacromolecular crystals

2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Saminathan Ramakrishnan ◽  
Jason R. Stagno ◽  
Valentin Magidson ◽  
William F. Heinz ◽  
Yun-Xing Wang
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Solid Phase ◽  
Control Element ◽  
Time Resolved ◽  
Crystalline Materials ◽  
Force Microscopy ◽  
Glass Surfaces

Solid–solid phase transitions (SSPTs) are widespread naturally occurring phenomena. Understanding the molecular mechanisms and kinetics of SSPTs in various crystalline materials, however, has been challenging due to technical limitations. In particular, SSPTs in biomacromolecular crystals, which may involve large-scale changes and particularly complex sets of interactions, are largely unexplored, yet may have important implications for time-resolved crystallography and for developing synthetic biomaterials. The adenine riboswitch (riboA) is an RNA control element that uses ligand-induced conformational changes to regulate gene expression. Crystals of riboA, upon the addition of a ligand, undergo an SSPT from monoclinic to triclinic to orthorhombic. Here, solution atomic force microscopy (AFM) and polarized video microscopy (PVM) are used to characterize the multiple transition states throughout the SSPT in both the forward and the reverse directions. This contribution describes detailed protocols for growing crystals directly on mica or glass surfaces for AFM and PVM characterization, respectively, as well as methods for image processing and phase-transition kinetics analysis.

Effects of pressure on the infrared spectra of some heterocyclic organosilicon and organogermanium compounds

1984 ◽  
Vol 37 (1) ◽  
pp. 23 ◽  
Author(s):  
SD Hamann ◽  
P Mazerolles ◽  
A Faucher ◽  
G Manuel
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Infrared Spectra ◽  
Functional Group ◽  
Organogermanium Compounds ◽  
Transannular Interaction

Measurements have been made of the infrared spectra of eight solid heterocyclic organosilicon and organogermanium compounds at pressures up to 5 GPa at normal temperature. Evidence is found of reversible conformational changes under pressure, and of phase transitions in some of the compounds. Unexpectedly, it appears that compression does not favour the transannular interaction that exists, in some cases, between the heteroatom (silicon or germanium) and a functional group on the opposite side of the ring.

Incommensurately modulated structure of morpholinium tetrafluoroborate and configurationalversuschemical entropies at the incommensurate and lock-in phase transitions

2017 ◽  
Vol 73 (5) ◽  
pp. 836-843
Author(s):  
Leila Noohinejad ◽  
Sander van Smaalen ◽  
Václav Petříček ◽  
Andreas Schönleber
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Ferroelectric Properties ◽  
Configurational Entropy ◽  
Chem Phys ◽  
Ambient Conditions ◽  
Disorder Phase Transition ◽  
The Difference ◽  
A Minor ◽  
Transition Entropy

Morpholinium tetrafluoroborate, [C4H10NO]+[BF4]−, belongs to a class of ferroelectric compoundsABX4. However, [C4H10NO]+[BF4]−does not develop ferroelectric properties because the incommensurate phase belowTc,I= 153 K is centrosymmetric with superspace groupPnam(σ100)00sand σ1= 0.42193 (12) atT= 130 K; the threefold superstructure belowTc,II= 117–118 K possesses the acentric but non-ferroelectric space groupP212121. At ambient conditions, [C4H10NO]+[BF4]−comprises orientationally disordered [BF4]−anions accommodated in cavities between four morpholinium cations. A structure model for the incommensurately modulated phase, which involves modulated orientational ordering of [BF4]−together with modulated distortions and displacements of the morpholinium ions is reported. A mechanism is proposed for the phase transitions, whereby at low temperatures morpholinium cations are shaped around the tetrafluoroborate anion in order to optimize the interactions with one orientation of this anion and, thus, forcing [BF4]−into this orientation. This mechanism is essentially different from a pure order–disorder phase transition. It is supported by consideration of the transition entropy. The difference in configurational entropy between the disordered and incommensurate phases has been computed from the structure models. It is shown to be much smaller than the experimental transition entropy reported by Owczareket al.[Chem. Phys.(2011),381, 11–20]. These features show that the order–disorder contribution is only a minor contribution to the transition entropy and that other factors, such as conformational changes, play a larger role in the phase transitions.

scholarly journals Synchronous RNA conformational changes trigger ordered phase transitions in crystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Saminathan Ramakrishnan ◽  
Jason R. Stagno ◽  
Chelsie E. Conrad ◽  
Jienyu Ding ◽  
Ping Yu ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Solid Phase ◽  
Lattice Order ◽  
Time Resolved ◽  
Rna Molecules ◽  
Cell Parameters ◽  
Force Microscopy ◽  
Synchronous Behavior ◽  
Induced Changes

AbstractTime-resolved studies of biomacromolecular crystals have been limited to systems involving only minute conformational changes within the same lattice. Ligand-induced changes greater than several angstroms, however, are likely to result in solid-solid phase transitions, which require a detailed understanding of the mechanistic interplay between conformational and lattice transitions. Here we report the synchronous behavior of the adenine riboswitch aptamer RNA in crystal during ligand-triggered isothermal phase transitions. Direct visualization using polarized video microscopy and atomic force microscopy shows that the RNA molecules undergo cooperative rearrangements that maintain lattice order, whose cell parameters change distinctly as a function of time. The bulk lattice order throughout the transition is further supported by time-resolved diffraction data from crystals using an X-ray free electron laser. The synchronous molecular rearrangements in crystal provide the physical basis for studying large conformational changes using time-resolved crystallography and micro/nanocrystals.

Phase Transitions and Conformational Changes in Monolayers of Human Apolipoproteins CI and AII

2003 ◽  
Vol 107 (40) ◽  
pp. 11117-11124 ◽  
Author(s):  
Jaime Ruiz-García ◽  
Abel Moreno ◽  
Gerald Brezesinski ◽  
Helmuth Möhwald ◽  
Jaime Mas-Oliva ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Conformational Changes

Schichteinlagerungsverbindungen des Niob- und Tantaldisulfids mit n-Alkylaminen / Layer Intercalation Compounds of Niobium and Tantalum Disulfide with n-Alkylamines

1973 ◽  
Vol 28 (3-4) ◽  
pp. 168-171 ◽  
Author(s):  
Robert Schöllhorn ◽  
Erwin Sick ◽  
Armin Weiss
Keyword(s):  
Phase Transitions ◽  
Conformational Changes ◽  
Interlayer Space ◽  
Alkyl Chain ◽  
Host Lattice ◽  
Guest Molecules ◽  
Amine Nitrogen ◽  
Alkyl Chains ◽  
Intercalation Complexes ◽  
Reversible Phase

NbS2 and TaS2 react with n-alkylamines to form intercalation complexes similar to those observed with TiS2. The arrangement of the guest molecules in the interlayer space is dominated by the interaction host lattice-amine nitrogen, if the alkyl chain of the amine contains 4 to 9 C-atoms. In complexes containing 12 to 18 C-atoms per alkyl chain, the van der Waals interaction between the alkyl chains is essentially responsible for the sterical arrangement of the intercalated molecules.Investigations with n-octadecylamine-NbS2 and oleylamine-NbS2 in the temperature range of 20-120°C lead to the observation of severval reversible phase transitions. These transitions are caused by conformational changes of the guest molecules as well as by changes in the ratio RNH2: NbS2.

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