The Olis Advantage: USA Stopped-Flow

For over 20 years, Dr. Richard J. DeSa and company have computerized hundreds of stopped-flows, ranging from the most ambitious commercial models to simple homemade versions.

When we decided to make our own stopped-flow, we were unprejudiced in our selection of 'best design features.' We evaluated all innovations and chose the better design in every instance; e.g., we found that vertically oriented syringes offer no advantages over horizontal syringes and, therefore, we stayed with the easier-to-view (and work with) horizontal arrangement. Furthermore, we are the only stopped-flow manufacturer who uses ceramic valves; we chose them because ceramic is inert, impervious to temperature extremes, and very hard (99% the hardness of diamonds). We also offer the only stopped-flow with a safety interlock system that provides 100% assurance against misfiring. And, Olis is renowned for customization, with projects such as fitting our stopped-flow inside magnets.

Company founder and inventor of the RSM 1000 and the USA stopped-flow, Dr. Richard J. DeSa, spent his post-doctoral years in Quentin Gibson's lab developing analog and digital computer software for high-speed data acquisition and analysis as applied to chemical kinetics and biochemical problems. During that time, DeSa computerized the first Gibson/Durrum stopped-flow. While at the University of Georgia's Department of Biochemistry, in addition to his duties as a tenured faculty member, DeSa studied the application of digital computer techniques to biochemical problems. He gained extensive experience in assembly language programming, data acquisition, and video data display.

DeSa's expertise in data collection and analysis was cited in H. Gutfreund's 1995 book, Kinetics for the Life Sciences.¹ In his discussion of the revolution in data collection, reduction, and analysis resulting from digitization and the use of PCs, Gutfreund states that, "The paper by DeSa and Gibson (1969) set a new trend for dealing with the output of instruments used for biochemical kinetics."² The paper to which Gutfreund referred, "A Practical Automatic Data Acquisition System for Stopped-Flow Spectrophotometry,"³ describes the authors' system of control and timing circuits used in conjunction with a digital computer to collect, analyze, and output data as applied to stopped-flow rapid-reaction spectrophotometry.

"It had been around fifteen years since I did stopped-flow. I was comfortable with the Olis in about an hour [working solo on a colleague's instrument]. The first shot filled the tubing. The second shot gave me partial kinetics. The third was the keeper. And the fourth shot confirmed the third. All in all, I used about 500 ul of solution." —Michael J. Barber, Ph.D., USF

Key Features of the U.S.A. Stopped-Flow

• Deadtime: 1-2 ms for absorbance and fluorescence (5-10 ms for CD)

• Valves: Fired Sapphire (inert, 99% the hardness of diamond, heat-resistant)t
  Low Volume Design: 40-70 µl/syringe/shot

• Mixer: Berger–Ball

• Pathlengths available: 20 mm, 10 mm, 4 mm; and (for CD) 2 mm

• Average Reagent Volume: 70-120 µl/syringe/shot; Low Volume Design: 40-70 µl/syringe/sho

• 100% assurance against misfiring or pre-mixing, by means of 5 sensors producing a fail-safe interlock system (active with and without Olis computer control)

• Drive syringes: SGE® glass syringes; low-temperature syringes also available. Standard: pair of 2.5 mL glass; choices: 0.5, 1, 2.5, and 5 for 1:1 to 1:11 mixing

• Tubing from valves to observation cell: Tefzel®, surgical stainless steel, or Teflon®

• Syringe extenders: PEEK® (polyetheretherketone), a polymer inert to almost all organic solvents.

• Observation chamber: quartz for absorbance and fluorescence models, stainless steel for low-temperature model.

• Syringe extenders: PEEK® (polyetheretherketone⁴)

• Large, convenient, indestructible knobs and dials

• Accessible ports with easy on/off fitting of water and gas lines to bath chamber for thermostatting and degassing of bath fluid and exposed syringe plungers.

• Floodable water bath chamber made of Delrin®⁵

• Pneumatic drive system: one plunger moves both syringe pistons simultaneously.

• Independent movement of syringes and valves for convenience in filling and flushing.

• Anodized cast-aluminum channel (0.5 cm thick) and optical railing (1 cm thick) for high structural integrity

• Weight: 18.6 pounds (8.45 kg)

• Perfect, tool-free alignment of stopped-flow observation ports within sample compartment of host spectrometer.

TEFLON®, Tefzel®, and DELRIN® are registered trademarks of E.I. duPont de Nemours & Company.
UNIMETRICS® is a registered trademark of Unimetrics Corporation.
PEEK® is a registered trademark of Victrex PLC.