W0117
Novel Crystal Structure of a Sodium and Potassium Nitrate
Obtained from the Leg of a Orthoptero of the Tridactylidae Family. J.
Ellenaa, E.E. Castellanoa, A. Ferreirab,
aInstituto de Física de São Carlos, USP, São Carlos
(SP). bInstituto de Biociências, UNESP, Rio Claro (SP)
BRAZIL.
We report here the X-Ray crystal structure of a Sodium and
Potassium Nitrate salt,
Na0.63K0.37NO3•H2O,
obtained from a rather peculiar and unexpected source. Evolution changes in
insects can be characterized by studying morphological variations in their legs,
and sometimes by other alterations like the presence of glands inside them as
has been widely reported. In this context, a recent study on a specimen of the
species Ellipes (Orthoptera- Trydactiloidea-Trydactilidae), collected in the
margin of the Araguaia River, in the Bananal Iland, showed the presence of a
cluster, in the insect of middle legs tibia, of what seemed to be small
crystals. The insects are only 1.5 to 3.0 mm in length and the crystals were
observed and photographed with an optical microscope. Although it is not the
principal aim of this report, it is interesting to point out that the crystals
are only present in the middle legs, never in the anterior or posterior legs,
and that the size and quantity of the crystals increase with insect age until
they occupy most of the interior of the leg. Because of the very small size of
the insect legs and the tiny amount of material, handling of the crystals turned
out to be a rather difficult task. A further complication was the tendency of
the samples to stick to the microscope glass slide. The crystals were very small
prisms and the largest found, with dimensions 0.010 x 0.005 x 0.001 mm, was used
for diffraction measurements. The shortest length could not be determined with
precision and 0.001 mm is just an upper estimation of its value. To prevent the
crystal from sticking to the microscope glass slide, it was soaked in glycerin
and then mounted in a 0.2 mm cryogenic loop protein support. Data collection on
an Enraf Nonius Kappa-CCD diffractometer proceeded at 100K during about 20hs.
The compound crystallizes in the trigonal space group R32 and was described in a
hexagonal cell with a = 4.811(1) and c =15.956(5) Å. The
structure was refined by full matrix least squares to a final R1 value of 0.075,
from 114 independent reflections with
I>2*σ(I).