The effect of simple shear flow on the helix-coil transition of poly-L-lysine

Lee, A. T.; McHugh, A. J.

doi:10.1002/(sici)1097-0282(199911)50:6<589::aid-bip3>3.0.co;2-3

Cited by 15 publications

(5 citation statements)

References 14 publications

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“…Aside from the difficulties associated with describing the shear in complicated flows, the choice of measure is itself problematic. Previous studies of flowinduced protein unfolding have used different parameters to describe the shear conditions, although shear rate is probably the most commonly used (4,9,17,25). However, if the magnitude of shear rate, rather than shear stress, was the instigator of the increased solvent exposure of side-chain residues, then one may expect to see similar changes occurring in water and in glycerol at the same flow rates, but this is not the case for this study.…”

Section: Resultsmentioning

confidence: 93%

Shear-Induced Unfolding of Lysozyme Monitored In Situ

Ashton

Dusting

Imomoh

et al. 2009

Biophysical Journal

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Conformational changes due to externally applied physiochemical parameters, including pH, temperature, solvent composition, and mechanical forces, have been extensively reported for numerous proteins. However, investigations on the effect of fluid shear flow on protein conformation remain inconclusive despite its importance not only in the research of protein dynamics but also for biotechnology applications where processes such as pumping, filtration, and mixing may expose protein solutions to changes in protein structure. By combining particle image velocimetry and Raman spectroscopy, we have successfully monitored reversible, shear-induced structural changes of lysozyme in well-characterized flows. Shearing of lysozyme in water altered the protein's backbone structure, whereas similar shear rates in glycerol solution affected the solvent exposure of side-chain residues located toward the exterior of the lysozyme alpha-domain. The results demonstrate the importance of measuring conformational changes in situ and of quantifying fluid stresses by the three-dimensional shear tensor to establish reversible unfolding or misfolding transitions occurring due to flow exposure.

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Section: Resultsmentioning

confidence: 93%

Shear-Induced Unfolding of Lysozyme Monitored In Situ

Ashton

Dusting

Imomoh

et al. 2009

Biophysical Journal

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“…87 Further studies, via real-time circular birefringence measurements, showed a reversible, shear-induced, helix-to-coil transition of poly-L-lysine in simple shear flow. 24 The conformational transition was observed at a critical strain rate of 300 s 21 , and the change was attributed to a shear-induced breakage of intramolecular hydrogen bonds in a-helical poly-L-lysine.…”

Section: Molecular Models and Theoretical Aspectsmentioning

confidence: 98%

“…By virtue of its conformational plasticity in response to temperature, pH, salt concentration and alcohol content in solution, 24 poly-L-lysine is commonly used as a model system in protein studies. 85 The homopolypeptide exists as a random coil at neutral pH, a-helix at high alkaline pH and b-sheet at temperatures [308C.…”

Section: Molecular Models and Theoretical Aspectsmentioning

confidence: 99%

The effects of shear flow on protein structure and function

Bekard

Asimakis

Bertolini³

et al. 2011

Biopolymers

175

140

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Toxoplasma gondii usually causes an asymptomatic and then latent infection in human adults; however, a potentially fatal disseminated form can occur in immunocompromised patients. Given that the diagnosis of acute Toxoplasma infection, as opposed to latent disease, relies on finding direct evidence of T. gondii infection in tissue, pathologic examination is critical. There have only been a few reports describing the cytomorphology of Toxoplasma in exfoliative cytology, and no reports of the findings in Thin Prep. In this report, we describe a fatal case of toxoplasmosis in a cardiac transplant patient that was diagnosed by respiratory cytopathology. Although the extracellular organisms were well visualized on the Wright‐Giemsa stained cytospin, they were only faintly seen on the Pap‐stained cytospin trapped within mucin and were not easily appreciated on the ThinPrep slides nor the H&E stained cell block sections. An immunohistochemical stain for Toxoplasma performed on the cell block was strongly positive, and an autopsy performed on the patient confirmed disseminated infection. Our case illustrates that the diagnosis of Toxoplasma in exfoliative cytology specimens can be challenging since organisms are not well visualized on ThinPrep or Pap‐stained material; therefore, Wright‐Giemsa stained material can be particularly helpful. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.

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“…In an ensuing paper, Lee and McHugh reported a reversible shear-induced helix-to-coil transition in dilute PLL samples originally in a helix-coil equilibrium. 36 They noted the occurrence of this transition above a critical shear rate of 300 s À1 in simple shear flow.…”

Section: Introductionmentioning

confidence: 96%