Code UG Weekly Notes 11-28-01

Physical Sciences Division
Weekly Highlights for Week Ending 11/28/2001

*** Indicates item is appropriate for the HQ senior staff and may appear
on the OBPR Web site: http://spaceresearch.nasa.gov

ISS FLIGHT PROGRAM

PHYSICS OF COLLOIDS IN SPACE (PCS) ON ISS: EXPPCS conducted two 48 hour
runs during the past week. The first was used to study the early stage
crystallization of the colloid-polymer crystal sample. The second run
was used primarily to assess the current state of aging of the colloid-polymer
gel sample with a 44 hour-long low angle dynamic scattering measurement.
Unfortunately, because of some miscommunication of the measurement parameters
between the science team and the ops team for the first 48 hour run, the
run resulted in data that did not cover the proper angular scattering
ranges to observe the desired behavior. Therefore, we plan to repeat this
run in the near future.

MICROGRAVITY RESEARCH PROGRAM OFFICE (MRPO) PAYLOAD OPERATIONS STATUS
ON THE INTERNATIONAL SPACE STATION (ISS) 7A.1 STAGE: Week 15 of Stage
7A.1 of ISS Increment 3 began with all MRPO payloads performing nominally.
This will be the last week of Increment 3. Joint Operations for Increment
4 will begin with the arrival of Flight UF1 (STS-108) on 12/1/01. Crew
attended operations will be significantly curtailed during the week of
11/26/01, (approximately 6 hours) due to preparations for the arrival
of UF1. All necessary work for Increment 5 and 6 payloads is in full stride.

SCIENCE HIGHLIGHTS

CROSS DISCIPLINE:

PAPER PRESENTED AT US-JAPAN CATARACT CO-OPERATIVE RESEARCH GROUP (CCRG)
MEETING: Dr. Rafat Ansari (NASA GRC) presented a paper "A New Instrument
for the Simultaneous Measurements of Dynamic Light Scattering and Natural
Fluoresence for the Early Detection of Cataracts" at the US-Japan
Cataract Co-operative Research Group (CCRG) Meeting, Hawaii, November
3-7, 2001. This paper, for the first time, presented a new instrument
which combines these two powerful techniques into one single instrument
for making simultaneous measurements. Preliminary data taken on human
subjects was presented showing a gradual increase in the degree of natural
fluorescence in the eye lens as a function of age in normal patients (20-55
years). Data was also presented on the preliminary trials of an anti-cataract
agent in rats. DLS can pick up the changes one day post treatment. The
conventional methods detects a mature cataract seven days post injection
at which time it is impossible to intervene with a drug.

FLUID PHYSICS PI REPORTS FIRST PROTEIN CRYSTALLIZATION ON GIANT LIPID
BILAYER VESCICLES: Fluid Physics Pi Prof. Alice Gast (Stanford) has successfully
extended their studies of two-dimensional (2D) protein crystallization
to investigate their behavior on the surfaces of giant lipid bilayer vesicles.
They carried out this work in collaboration with R. Merkel and E. Sackmann
at the Technical University of Munich. It is well known that some cell
surfaces have densely packed organized protein coatings such as S-Layer
proteins. They wished to study the influence of ordering on the surface
of synthetic lipid vesicles on their mechanical properties. In particular,
they have shown that streptavidin can successfully be crystallized into
large domains on biotinylated vesicles. Streptavidin has previously been
crystallized onto various 2D surfaces including lipid monolayers, supported
lipid bilayer, lipid nanotubes, and nanometer-sized lipid vesicles. To
their knowledge, this is the first report of any protein crystallization
on giant lipid bilayer vesicles (typically 20-60 microns in diameter).
In this study, they coated the vesicles either with pure streptavidin,
or a mixture of streptavidin and the homologous non-crystallizable protein
avidin. Vesicles that were coated with pure streptavidin, become covered
with protein crystals. The strong interaction between the protein and
the lipid membrane, in conjunction with the rigidity of 2D streptavidin
crystals, distorted the vesicle shapes. The vesicles show either faceted
spherical or spheroidal shapes, presumably affected by the nucleation
and growth rates of individual crystallites. In either case, the vesicles
exhibit viscoelastic behavior and show permanent plastic deformation when
stressed beyond the yield point. The ellipsoidal vesicles show a very
narrow aspect ratio (length/width) of 1.24 ± 0.11. Due to the interfering
effect of gravity flattening the vesicles horizontally, the precise value
of the preferred radius of curvature cannot be determined.