Two complementary β-sheet-forming decapeptides have been created that form binary self-repairing hydrogels upon combination of the respective free-flowing peptide solutions at pH 7 and >0.28 wt%. The component peptides showed little structure separately but formed extended β-sheet fibres upon mixing, which became entangled to produce stiff hydrogels. Microscopy revealed two major structures; thin fibrils with a twisted or helical appearance and with widths comparable to the predicted lengths of the peptides within a β-sheet, and thicker, longer, interwoven fibres that appear to comprise laterally-packed fibrils. A range of gel stiffnesses (G' from 0.05 to 100 kPa) could be attained in this system by altering the assembly conditions, stiffnesses that cover the rheological properties desirable for cell culture scaffolds. Doping in a RGD-tagged component peptide at 5 mol% improved 3T3 fibroblast attachment and viability compared to hydrogel fibres without RGD functionalisation.

Inducing opposite screw senses at the two ends of a helix traps a helix reversal, allowing it to be characterised spectroscopically.

Helical α-aminoisobutyric acid (Aib) foldamers show great potential as devices for the communication of conformational information across phospholipid bilayers, but determining their conformation in bilayers remains a challenge. In the present study, Raman, Raman optical activity (ROA), infrared (IR) and vibrational circular dichroism (VCD) spectroscopies have been used to analyze the conformational preferences of Aib foldamers in solution and when interacting with bilayers. A 3 -helix marker band at 1665-1668 cm in Raman spectra was used to show that net helical content increased strongly with oligomer length. ROA and VCD spectra of chiral Aib foldamers provided the chiroptical signature for both left- and right-handed 3 -helices in organic solvents, with VCD establishing that foldamer screw-sense was preserved when the foldamers became embedded within bilayers. However, the population distribution between different secondary structures was perturbed by the chiral phospholipid. These studies indicate that ROA and VCD spectroscopies are valuable tools for the study of biomimetic structures, such as artificial signal transduction molecules, in phospholipid bilayers.

Intraoperative assessment of surgical margins remains one of the main challenges in cancer surgery. Raman spectroscopy can detect cancer cells with high accuracy, but it is time-consuming. In this paper, we investigated a selectivesampling Raman spectroscopy approach, based on high wavenumber (HW) Raman imaging (spectral range 2,500-3,500 cm −1) and fingerprint Raman spectroscopy (spectral range 600-1,800 cm −1), to reduce the overall tissue analysis time while maintaining high diagnostic accuracy. HW Raman mapping was used as a first step to identify the adipose tissue regions based on the C-H stretching bands at 2,700-2,950 cm −1. As residual tumors are typically found in nonadipose tissue, an algorithm was developed to allocate sampling points for fingerprint Raman spectroscopy at locations corresponding to low intensity in the HW-Raman maps. Preliminary results show that HW-Raman imaging based on a 671 nm laser is effective and fast for mapping of adipose tissue in breast resections, with typical imaging times of 2 min for tissue areas as large as 2 × 2 cm 2 areas. Albeit the remaining high fluorescence background in the fingerprint region prevents the use of single 671-nm laser, the HW Raman imaging can be still exploited in combination with 785-nm excitation Raman spectroscopy for identifying residual tumor. Although this study demonstrates the feasibility of this approach, further improvements, such as using single element detectors for HW Raman imaging, are required to increase the analysis speed further towards intraoperative use in the routine clinical setting.

Histidine is a key component of a number of enzymatic mechanisms, and undertakes a myriad of functionalities in biochemical systems. Its computational modelling can be problematic, as its capacity to take on a number of distinct formal charge states, and tautomers thereof, is difficult to capture by conventional techniques. We demonstrate a means for recovering the experimental Raman optical activity (ROA) spectra of histidine to a high degree of accuracy. The resultant concordance between experiment and theory is of particular importance in characterising physically insightful quantities, such as band assignments. We introduce a novel conformer selection scheme that unambiguously parses snapshots from a molecular dynamics trajectory into a smaller conformational ensemble, suitable for reproducing experimental spectra. We show that the "dissimilarity" of the conformers within the resultant ensemble is maximised and representative of the physically relevant regions of molecular conformational space. In addition, we present a conformer optimisation strategy that significantly reduces the computational costs associated with alternative optimisation strategies. This conformer optimisation strategy yields spectra of equivalent quality to those of the aforementioned alternative optimisation strategies. Finally, we demonstrate that microsolvated models of small molecules yield spectra that are comparable in quality to those obtained from ab initio calculations involving a large number of solvent molecules.

The standard treatment for breast cancer is surgical removal mainly through breast-conserving surgery (BCS). We developed a new technique based on auto-fluorescence (AF) spectral imaging and Raman spectroscopy for fast intraoperative assessment of excision margins in BCS. A new wide-field AF imaging unit based on total internal reflection (TIR) was combined with a Raman spectroscopy microscope equipped with a 785 nm laser. The wavelength of the AF excitation was optimized to 365 nm in order to maximize the discrimination of adipose tissue. This approach allows for the non-adipose regions of tissue, which are at a higher risk of containing a tumor, to be targeted more efficiently by the Raman spectroscopy measurements. The integrated TIR-AF-Raman was tested on small tissue samples as well as fresh wide local excisions, delivering the analysis of the entire cruciate surface of BCS specimens (5.1 × 7.6 cm 2 ) in less than 45 minutes and also providing information regarding the location of the tumor in the specimen. Full automation of the instrument and selection of a faster translation stage would allow for the measurement of BCS specimens within an intraoperative time scale (20 minutes). This study demonstrates that the TIR-AF Raman microscope represents a feasible step towards the development of a technique for intraoperative assessment of large WLE within intraoperative timescales.

The early stages of fibril formation are difficult to capture in solution. We use cold-ion spectroscopyt oe xamine an 11-residue peptide derived from the protein transthyretin and clusters of this fibre-forming peptide containing up to five units in the gas phase.F or each oligomer,t he UV spectra exhibit distinct changes in the electronic environment of aromatic residues in this peptide compared to that of the monomer and in the bulk solution. The UV spectra of the tetraand pentamer are superimposable but differ significantly from the spectra of the monomer and trimer.S uchaspectral evolution suggests that acommon structural motif is formed as early as the tetramer.The presence of this stable motif is further supported by the low conformational heterogeneity of the tetraand pentamer,r evealed from their IR spectra. From comparison of the IR-spectra in the gas and condensed phases,w e propose putative assignments for the dominant motif in the oligomers.Parkinsons, Alzheimers, Huntingtons, diabetes type 2, familial amyloid polyneuropathy,and about 38 other diseases have been associated with the deposition of insoluble proteinaceous material in tissues.[1] In those insoluble deposits,p roteins are packed into fibrillar structures rich in bsheets,which are known as amyloid fibres.[2] Recent evidence suggests that the cytotoxic species are found amongst soluble, prefibrillar aggregates.[1] Since aggregation into amyloid fibres is am ulti-faceted process,avariety of techniques have been applied to assess both the kinetics of assembly and the macroscopic details of assembled fibrils.Despite the vast amount of information regarding the kinetics of fibrillation and the structure of mature fibrils,r elatively little is known about the structure of the soluble,prefibrillar,and potentially toxic aggregates.[1] Early events in fibrillogenesis feature adynamic,heterogenously populated ensemble of oligomeric states.Because of their inherently transient nature,their exact characterisation proves difficult using bulk solution and solidstate techniques.[3] To address this,gas-phase techniques,such as mass spectrometry coupled with ion mobility spectrometry (IM-MS), have particular relevance to enable size-specific characterisation of these transient ensembles.[4] Although mass spectrometry enables the selection of single oligomeric states,i tr emains ac hallenge to simultaneously examine changes in secondary structure at the intact protein level. Instead, peptide segments are often used as surrogates for proteins,allowing more details to be discerned regarding the conformational changes as aggregation proceeds.I narecent study,f or instance,acombination of IM-MS and IR spectroscopy revealed as ignature of b-sheet formation in gasphase oligomers of an insulin hexapeptide fragment. [5] Although the use of short isolated fragments greatly increases the capacity of IM-MS and spectroscopy to discern structural features,aquestion arises of whether the use of small peptides is appropriate for modelling the process of amyloid ...

One of the main challenges in cancer surgery is to ensure the complete excision of the tumour while sparing as much healthy tissue as possible. Histopathology, the gold-standard technique used...