NEWS
Undergraduate Awardees Receive ANALYTICAL CHEMISTRY The ACS Division of Analytical Chemistry has announced that 397 students have been chosen as winners of the 198990 undergraduate awards in analytical chemistry. The awards are given annually to chemistry students at U.S. colleges and universities to recognize outstanding scholastic achievement and to stimulate interest in the field of analytical chemistry. Awardees will receive 16 is sues of A N A L Y T I C A L C H E M I S T R Y (October 1989 to May
1990) and the Division newsletter. The winners were select ed by the faculties of the chemistry departments of their respective institutions.
Hearing the Faintest Noise Cornell University biophysicists have reported that struc tures in a frog's ear respond to the faint, pervasive back ground noise from the random collisions of molecules. Like other experiments that established that the eye's photo receptor cells can detect single photons or that the nose's chemical receptors will respond to single molecules, these results set lower limits for "hearing." The researchers, Winfried Denk and Watt Webb, mea sured the mechanical motion of hairbundles inside the frog's inner ear that respond to sound waves, and the corre sponding electrical response from hair cells attached to the bundles. Similar structures are found in many organisms, including humans. Webb and Denk used a laser differential microinterferometer to record the hairbundle motion. The microinterferometer consisted basically of two matched laser beams ca pable of detecting motions of approximately 1 pm/s. Out put voltages from the hair cells were monitored by microelectrodes. With this experimental setup, the Cornell researchers demonstrated that hair cells produced signals that precise ly correlated with the spontaneous motion of the hairbundles (about 1 nm) due to thermal noise. Says Webb, "While we still do not fully understand how this important transducer works at the molecular level, we now possess key information about its abilities."
Sugar-Coated Semiconductors Researchers led by Mark Bednarski of the University of California at Berkeley and the Lawrence Berkeley Labora tory are investigating how the common bacterium E. coli attaches to silicon wafers coated with various types of or ganic molecules. Determining whether biological organisms adhere to surfaces will be important in designing new ma terials and coatings that resist biofouling. This information may also help in the study of infections triggered by the binding of bacteria and viruses to cell surfaces. In the experiments, semiconductor surfaces are coated with alcohols, lipids, sugars, organic acids, and bases. With ANALYT
all but the sugars, adhesion is nonspecific; bacteria have a stronger hold on the semiconductor surface as acidity, hydrophilicity, and electric charge increase. Bacteria with specific receptors for the sugars mannose and galactose bind to wafers with these sugars, but not to those coated with glucose. The California scientists characterized the wafer surfaces with X-ray photoelectron spectroscopy, ellipsometry, and scanning electron microscopy (SEM). A contact angle mea surement, related to hydrophilicity, predicts whether bac teria will nonspecifically adhere to the surface. Surfaces whose contact angles are less than 30° exhibit the best ad hesion, as demonstrated by SEM. Says Bednarski, "Now we have a system to study the conformation and composi tion of cell-surface molecules, which is not possible by strictly biological techniques."
Implantable Glucose Monitor Every day an estimated 1 million Americans with Type I insulin-dependent diabetes prick their fingers to monitor blood glucose levels. In time, the finger pricking could de stroy nerve endings, robbing the finger of all sensation. A new implantable glucose sensor now under development can perform the same measurement more accurately, with little or no physical discomfort. The device, labeled the Rechargeable Physiological Sen sor (RePS), is being developed by Ebtisam Wilkins and her co-workers at the University of New Mexico's Department of Chemical and Nuclear Engineering and by Wade Rad ford and engineers at the Johns Hopkins University's Ap plied Physics Laboratory (APL). The collaborators plan to complete a prototype this year and predict that a commer cial unit will be marketed in about four years. The sensor, designed by Wilkins, consists of a polyvinyl coating impregnated with an ionic glucose salt wrapped around a P t electrode. Changes in glucose concentration shift the equilibrium between the associated and dissociat ed forms of the glucose salt, which is monitored electrochemically. A hydrogel or membrane coating prevents leaching of the salt. When implanted just under the skin in the abdominal re gion, the RePS measures changes in tissue glucose levels. According to Wilkins, the tissue levels lag about 20 min be hind blood glucose values. A lithium battery-powered telemetry system built by APL transmits the glucose information to a hand-held re ceiving unit. The RePS is also rechargeable, unlike most other sensors currently under development.
For Your Information The American Association for Clinical Chemistry (AACC) has issued a guide for employers setting up "blind" em ployee drug testing programs. Employer's Guide to Evaluating Laboratory Performance is available from AACC, 2029 Κ Street, N.W., Seventh Floor, Washington, DC 20006 (202-857-0717; 835-8744). CHEMISTRY, VOL. 61, NO. 19, OCTOBER 1, 1989 · 1077 A
