The α-Helix to β-Sheet Transition in Stretched and Compressed Hydrated Fibrin Clots

Abstract

Fibrin is a protein polymer that forms the viscoelastic scaffold of blood clots and thrombi. Despite the critical importance of fibrin deformability for outcomes of bleeding and thrombosis, the structural origins of the clot's elasticity and plasticity remain largely unknown. However, there is substantial evidence that unfolding of fibrin is an important part of the mechanism. We used Fourier transform infrared spectroscopy to reveal force-induced changes in the secondary structure of hydrated fibrin clots made of human blood plasma in vitro. When extended or compressed, fibrin showed a shift of absorbance intensity mainly in the amide I band (1600-1700 cm(-1)) as well as in the amide II and III bands, indicating an increase of the β-sheets and a corresponding reduction of the α-helices. The structural conversions correlated directly with the strain or pressure and were partially reversible at the conditions applied. The additional absorbance observed at 1612-1624 cm(-1) was characteristic of the nascent interchain β-sheets, consistent with protein aggregation and fiber bundling during clot deformation observed using scanning electron microscopy. We conclude that under extension and/or compression an α-helix to β-sheet conversion of the coiled-coils occurs in the fibrin clot as a part of forced protein unfolding.

Composite of porous starch-silk fibroin nanofiber-calcium phosphate for bone regeneration

“…Regenerated SF consists of three kinds of protein structure; ȕ-sheet, Į-helix, and random coil. The type of secondary structure in proteins can be determined based on the absorption associated with amide I (C=O stretching), amide II (N-H bending), and amide III (N-H bending and C-N stretching) in IR spectra [16,17]. As shown in Fig.…”

“…Fourier Transform Infrared Spectroscopy in the Attenuated Total Reflectance mode (FTIR-ATR, Equimo55 bruker FTIR spectrometer) was used to examine the SF structural changes during electrospinning in methanol coagulation bath. The quantitative analysis of amide I absorption band within the 1600-1700 cm -1 region [16,17], was done using curve-fitting and de-convolution methods to determine the amount of Į-helix, ȕ-sheet, and random coil elements in each spectrum.…”

Fibrin Networks Support Recurring Mechanical Loads by Adapting their Structure across Multiple Scales

“…There is already evidence of force-induced conformational changes (47) and unfolding of fibrin monomers (15) under mechanical loading, which may be responsible for the dissipative remodeling. Here, coarse-grained simulations are likely needed to connect molecular-scale insights from full-atom simulations to macroscale mechanics at the protofibril and fiber levels.…”

Thermal gelation or gel melting: (ethylene glycol)113‐(l‐alanine)12 and (ethylene glycol)113‐(l‐lactic acid)12

“…The main characteristic amide I band was observed at 1650 cm 21 , which is related to the a-helical structure. 31,32 There was no significant change in the CAH stretching band (2800-3000 cm 21 ) of PEG-PA in FTIR [ Fig. 8(a)].…”