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Jean Collins
Jean Collins

Lattice 1.8.5


By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8+/-0.09 nm in diameter and 1.9+/-0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40-60 nm, and a range of 1.8-5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12-40 nm for their diameter and 0.7-2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 microm(2). According to their size, we classified the invaginated pits into two types--larger pits measuring 139 nm in diameter and 7.2 nm in depth, and smaller pits measuring 96 nm in diameter and 2.3 nm in depth. On dehydration-induced dead protoplasts, the degree of polarization of plasma membranes decreased. Lipid molecular layers appeared relatively smooth, and the quantity of integral proteins reduced a lot. Invaginated pits were still detectable at the membrane surface, but due to dehydration-induced protoplast contraction, the orifice diameter of pits reduced, and their depth increased. Larger pits averagely measuring 47.4 nm in diameter and 31.9 nm in depth, and smaller pits measuring 26.5 nm in diameter and 43 nm in depth at average. The measured thickness of plasma membranes of mesophyll cells from winter wheat examined by AFM was 6.6-9.8 nm, thicker in regions covered with proteins.




Lattice 1.8.5


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Pointlessscores all the possible Laue groups consistent with the crystalclass, which is based on cell dimension restraints. It does this bymatching potential symmetry equivalent reflections. For chiralsystems, the Laue group uniquely implies the point group. It thenchecks sets of reflections which may be systematically absent tosuggest a possible spacegroup. There is also a check for latticecentering, ie a check for whole classes of reflections havingessentially zero intensity, including a check for obverse/inverse twinning in rhombohedral systems.[Note:strictly speaking, the program determines the Patterson group ratherthan the Laue group, since the Laue group is a point group, notincluding any lattice centring type (P,C,I,F,H,R). Lattice centringis included in the reported Laue group, andreindexing from the original setting may change the latticetype.]The principal (test) reflection input is taken fromone or more unmerged MTZ files (HKLIN) such as those from Mosflm (orCombat), or alternatively unmerged XDS ASCII files (XDS_ASCII orINTEGRATE, XDSIN), unmerged Scalepack files(SCAIN) (produced with the Scalepack option "nomerge originalindex"), SHELX files (also SCAIN) or SAINT files (also SCAIN).Also free-format files containing HKL I sigI (see SCAIN). Input types may be mixed. Merged files may be checked for under-merging& for systematic absences. Files given as HKLIN will be checked fortheir filetype, so other types will be recognised. For some crystalclasses and when there is more than one input file, it is necessaryto establish first that a consistent indexing convention has beenused for all runs (see an explanation and list). Note that if there are multiple inputfiles and no reference file, the first input file is used as atemporary reference for subsequent files, to check for consistentindexing in cases of ambiguity.This may not work correctly ifthis first file is indexed in the wrong Laue group: the keyword TESTFIRSTFILEmay be used to force a Laue group check on the first file beforeadding in the others.


Multilattice files from Mosflm/FECKLESS can be read: the differentlattices are for now (pending refactoring of the data objects) aremapped into different runs, with BATCH numbers incremented by multiplesof 1000 (in FECKLESS). By default only the first Run, corresponding tothe first Lattice, is used in symmetry determination, but all runs arewritten to the output HKLOUT file. Other runs may be selected with the USE command.


AllLaue groups which are sub-groups of the lattice group aregenerated by combining pairs of symmetry elements (including theidentity) and completing the groups. For merged files, sub-groups ofthe merged symmetry are excluded, The sub-groups are then scored bycombining the scores for the individual elements, counting scores forelements present in the sub-group as positive & those elements notin the sub-group as negative. It is not clear what is the best way of combining the element scores:at present two scores are printed


The default CELL-BASED option also affects the Laue group settingfor centred monoclinic lattices: in this case the body-centredsetting (I 1 2/m 1, eg space group I2) will be chosen if it leads toa less oblique cell (smaller beta angle) than the C-centred setting(C 1 2/m 2, eg space group C2). The SYMMETRY-BASED or C2 options willalwaysselect the C2 setting.


Tolerance in degrees for determination of lattice symmetry[default 2 degrees]. Tolerance is the maximum deviation from theexpected angle between two-fold axes in the lattice group, eg for aputative tetragonal lattice where a=b, the expected angle betweenthe diagonals is 90 degrees, and the deviation delta =2tan^-1(a/b) - 90When testing alternative indexing schemes tomatch HKLIN to HKLREF datasets, this angular tolerance is convertedto a "average length" tolerance by multiplying by theaverage cell edge.


Search for centre of symmetry in the lattice. This should be atindex 0,0,0, but occasionally the pattern has been misindexed, eg by+-1 along the rotation axis. This option performs an R-factor (Rmeas)search around 0,0,0, by default for +-2 grid points in eachdirection (the size of the search grid may be reset to hgrid,kgrid, lgrid here). The lowest R should be at 0,0,0. Note that if theLaue group symmetry is wrong, this search may be less reliable: aLAUEGROUP command may be given to reset the symmetry. If an HKLOUTfile is specified, the reindexed data is written (even if thereindexing operator is the identity).


The archetypal solvolysis reaction is the reaction with water, i.e., hydrolysis, (\ref1.8.5). However, solvolysis is a general reaction, involving bond breaking by the solvent. Thus, the reaction with ammonia is ammonolysis, (\ref1.8.6), the reaction with acetic acid is acetolysis, (\ref1.8.7), and the reaction with an alcohol is alcoholysis, (\ref1.8.8) where Et = \(\ceC2H5\). In each case the same general reaction takes place yielding the cation associated with the solvent.


Since silver nitrate and barium nitrate are soluble in both solvents, the differences must be due to differences in the solubility of the chlorides in each solvent. A consideration of the relative stability of solid silver chloride versus the solvated species (Figure \(\PageIndex1\).61) shows that the enthalpy of solvation in water is less than the lattice energy. Thus, if silver chloride were present as Ag+ and Cl- in water it would spontaneously precipitate. In contrast, the enthalpy of solvation in ammonia is greater than the lattice energy, thus solid AgCl will dissolve readily in liquid ammonia. The reason for the extra stabilization from the specific solvation of the silver cation by the ammonia, i.e., the formation of the covalent complex [Ag(NH3)2]+.


As may be seen from Figure \(\PageIndex1\).62, the opposite effect occurs for barium chloride. Here the enthalpy of solvation in ammonia is less than the lattice energy. Thus, if barium chloride were present as Ba2+ and Cl- in ammonia it would spontaneously precipitate. In contrast, the enthalpy of solvation in water is greater than the lattice energy, thus solid BaCl2 will dissolve readily in water. The stabilization of Ba2+(aq) occurs because water will have a larger sphere of non-specific solvation as a consequence of having two lone pairs, allowing interaction with the Ba2+ as well as other water molecules (Figure \(\PageIndex1\).63). 041b061a72


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