### Session B2: Biophysics

Chair: Bethe Scalettar, Lewis and Clark
Room: Miller 102

 Friday, May 16, 2008 2:00PM - 2:36PM B2.00001: The Role of Cryoprotectants in the Successful Cryogenic Cooling of Protein Crystals Invited Speaker: Douglas Juers Protein crystals for high resolution X-ray structure determination are typically cooled to $\sim$100K prior to X-ray exposure to minimize crystal damage from the ionizing radiation. However, cooling itself can damage the crystal. This cooling-induced damage can be minimized by adding small molecules, called cryoprotectants, to the disordered phase that permeates the interstices between the protein molecules in the crystal lattice. The cryoprotectants appear to minimize cooling-induced damage by adjusting the thermal contraction of the disordered phase to match the thermal contraction of the protein crystal lattice. We will discuss our recent experiments in characterizing the thermal contraction of cryoprotective solutions in order to develop predictive capabilities for potential cryoprotectants. We measured the thermal contraction caused by binary solutions between water and 20 different cryoprotectants. At a concentration of 50{\%} (w/w), these solutions contracted over a range of 0-15{\%}. To develop predictive capabilities we looked for easily measured physical properties of the pure cryoprotectants that were well correlated with the observed thermal contraction. While viscosity, vapor pressure, molecular weight and the water-octanol partitioning were all reasonably correlated with the thermal contraction, the best predictor of the thermal contraction of the cryosolution was the number of hydroxyls in the cryoprotective molecule. Friday, May 16, 2008 2:36PM - 2:48PM B2.00002: A Contactless Capacitance Detection System for Microchip Capillary Electrophoresis Peter Wu The design, construction and operation of a simple, inexpensive and compact high voltage power supply for use in conjunction with a simple cross, capillary electrophoresis microchip is presented. The detection system utilizes a single high voltage power supply (15 kV), a voltage divider network for obtaining the required voltages for enabling a gated injection valve, and two high voltage relays for switching between the open and closed gate sequences of the injection. The system is used to determine sodium monofluoroacetate (MFA) concentration in diluted fruit juices and tap water. A separation buffer consisting of 20 mM citric acid and histidine at pH 3.5 enabled the detection of the anion in diluted apple juice, cranberry juice, and orange juice without lengthy sample pretreatments. Limit of detection in diluted juices and tap water were determined to be 125, 167, 138, and 173 mg/L for tap water, apple juice, cranberry juice, and orange juice, respectively, based upon an S/N of 3:1. The total analysis time for detecting the MFA anion in fruit juices was less than 5 min, which represents a considerable reduction in analysis time compared to other analytical methods currently used in food analysis. Friday, May 16, 2008 2:48PM - 3:00PM B2.00003: Studying Light Propagation in Bone for Treatment of Bone Cancers with Photodynamic Therapy Vincent Rossi , Scott Gustafson , Steven Jacques Photodynamic therapy makes use of light, photosensitizing agents, and oxygen as a selective means of treating cancer. The work presented is aimed at applying photodynamic therapy towards treatment of osteosarcoma in small animal clinics. To best facilitate clinical treatments, we must first understand how light propagates and how best to deliver adequate light to achieve phototoxic effects within bone. This work aims at characterizing how light propagates through bone and then applying that knowledge towards predicting light distributions in bone. Reflectance spectroscopy using an optical fiber source-collector pair is used to determine the scattering properties of bone tissues, and the absorption due to water and oxygenated and deoxygenated hemoglobin---native absorbers at visible and near-IR wavelengths. Resulting optical characterizations are then applied to a cylindrically symmetric Monte Carlo model in order to predict and guide the delivery of light within bone in order to achieve the desired phototoxic effect. Friday, May 16, 2008 3:00PM - 3:12PM B2.00004: Characteristics of Waves in Plants Orvin Wagner In my older literature I didn't recognize that plant frequencies are isotropic. I use the idea, however, in equating vertical and horizontal frequencies to get vertical to horizontal velocity ratios. In these calculations I use averages of reciprocals of representative samplings of vertical and horizontal internodal spacings A$_{v}$ and A$_{h}$. The resultant equation is v$_{v}$A$_{v}$=v$_{h}$A$_{h }$or v$_{v}$/v$_{h}$=A$_{h}$/A$_{v}$. These velocity ratios can also be obtained by direct measurement or by taking ratios of needles per unit length in some cases. These ratios are related to the shape of the plant due to gravity interaction, for example for p.pine 3/1 or for apple 4/3. The velocity increases with the plant part's angle to the horizontal. It is possible that waves in plants are related to sound like waves in WIMPS (if WIMPS are the actual particle) because of their very low velocities (larger than ionic velocities, near 5 m/s outside of plants, 1.25 m/s on sun's surface) both inside and outside of plants. Some object to my approach because they say the WIMP density could not be large enough on the earth's surface. My experiments seem to suggest otherwise. See 1999 Physics Essays 12:3-10 and my website home.budget.net/$\sim$oedphd. Friday, May 16, 2008 3:12PM - 3:24PM B2.00005: Elucidating Molecular Events Underlying Learning with Fluorescence Microscopy Bethe Scalettar , Mariya Chavarha , Janis Lochner Unraveling the molecular processes that underlie learning remains one of the most intriguing, unresolved problems in science. Learning and memory formation are believed to reflect alterations in the connections among nerve cells. These alterations are driven in part by proteins that are secreted from the surface of nerve cells. The secreted proteins act locally to mediate changes in nerve cell connectivity. Molecular processes, such as protein secretion, that underlie learning can be studied in living cells using high-resolution, time-lapse fluorescence microscopy. In this technique, proteins of interest, such as those mediating learning, are fluorescently labeled using genetic engineering, and then living cells containing the labeled proteins are imaged as a function of time using high-resolution fluorescence microscopy. In this talk, we will discuss both our biophysical approach and some recent insights that we have obtained using this approach into pivotal processes that underlie learning. Friday, May 16, 2008 3:24PM - 3:36PM B2.00006: Quantum Capillary Action Richard Kriske For many years it has been widely accepted that Capillary Action as seen in plants was best calculated using a classical method. Recent experiments with carbon nanotubes seem to suggest that a Quantum Mechanical explanation may now be appropriate. The suggested use of Carbon nanotubes as steering mechanisms for particle accelerators may reveal a better model using Quantum mechanics. Friday, May 16, 2008 3:36PM - 3:50PM B2.00007: BREAK