This review focuses on selected applications of the separation and analysis of peptides and proteins published during the period of 1997-1998. Specific topic areas covered include high-performance liquid chromatography (HPLC), ultrafiltration, capillary electrophoresis (CE), affinity-based methods for protein isolation and separation, mass spectrometry (MS), detection of nonenzymatic posttranslational modifications, nuclear magnetic resonance spectroscopy (NMR), infrared (IR) and Raman spectroscopy, circular dichroism (CD), UV-visible absorption spectroscopy, dynamic light scattering, and calorimetry. The quantification and identification of peptides and proteins by chromatographic methods and MS have become fairly routine, as has the conformational analysis of peptides and small proteins in solution by CD, IR, and NMR. Therefore, these topics are not reviewed in detail here. In this review, we have attempted to highlight new technological developments or unique applications of analytical methods that impact the analysis of peptides and proteins.

A B S T R A C TDrag reduction by marine organisms has undergone millions of years of natural selection, and from these organisms biomimetic studies can derive new technologies. The shortfin mako (Isurus oxyrinchus), considered to be one of the fastest and most agile marine predators, is known to have highly flexible scales on certain locations of its body. This scale flexibility is theorized to provide a passive, flow-actuated mechanism for controlling flow separation and thereby decreasing drag. Recent biological observations have found that the shortfin mako has highly flexible scales, bristling to angles in excess of 50°, particularly on the sides of the body downstream of the gills. High "contragility," which is explicitly defined here as the ability to change or move in a new or opposing direction while already in a turn, would occur if form drag were minimized. This would thus indicate the potential control of flow separation on body regions aft of the point of maximum girth or in regions of adverse pressure gradient. Thus results are consistent with the hypothesis that scale bristling controls flow separation. This scale flexibility appears to be a result of a reduction in the relative size of the base of the scales as well as a reorganization of the base shape as evidenced by histological examination of the skin and scales. Probable mechanisms leading to separation control are discussed.

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Over many decades the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow which appear on surfaces such as shark skin, have been well documented. However the skin of dolphins is embedded with sinusoidal grooves that run perpendicular or transverse to the flow over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus acting as a potential mechanism to reduce flow separation and thus pressure drag. In an attempt to test this hypothesis and study these effects, an adverse pressure gradient was induced above a flat plate resulting in a controlled region of flow separation occurring within a tripped, turbulent boundary layer. Small transverse grooves of both rectangular and sinusoidal shape were 3D printed and mounted to the plate to measure their effect on the boundary layer flow. The results were compared to a flat plate without grooves using digital particle image velocimetry (DPIV). The strength of the adverse pressure gradient was varied, and the observed control in flow separation and other effects upon the boundary layer are discussed.

Abstract. The Shortfin Mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility, and has flexible scales known to bristle up to 50 0 in the flank regions. It is purported that this bristling capability of the scales may result in a unique pass flow control method to control flow separation and reduce drag. It appears that the scales have evolved to be only actuated when the flow over the body is reversed; thereby inducing a method of inhibiting flow reversal close to the surface. In addition, bristled scales form cavities which could induce boundary layer mixing and further assist in delaying flow separation. To substantiate the hypothesis, samples of skin from the flank region of the mako have been tested in a water tunnel facility under various strengths of adverse pressure gradient (APG). Laminar and turbulent separation over the skin was studied experimentally using Time-Resolved Digital Particle Image Velocimetry (TR-DPIV), where the APG was generated and varied using a rotating cylinder. Shark skin results were compared with that of a smooth plate data for a given amount of APG. Both the instantaneous and time-averaged results reveal that shark skin is capable of controlling laminar as well as turbulent separation. Under laminar conditions, the shark skin also induces an early transition to turbulence and reduces the degree of laminar separation. For turbulent separation, the presence of the shark skin reduces the amount of backflow and size of the separation region. Under both flow conditions, the shark skin also delayed the point of separation as compared to a smooth wall.