Mehedi Reza

Aalto University

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Structure of wood cell wall based on high-resolution transmission electron microscopy

Mehedi Reza Tapani Vuorinen Janne Ruokolainen

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Interactions between lipid-free apolipoprotein-AI and a lipopeptide incorporating the RGDS cell adhesion motif

Nanoscale (2014)

Valeria Castelletto Ian W. Hamley Mehedi Reza Janne Ruokolainen

The interaction of a designed bioactive lipopeptide C16-GGGRGDS, comprising a hexadecyl lipid chain attached to a functional heptapeptide, with the lipid-free apoliprotein, Apo-AI, is examined. This apolipoprotein is a major component of high density lipoprotein and it is involved in lipid metabolism and may serve as a biomarker for cardiovascular disease and Alzheimers' disease. We find via isothermal titration calorimetry that binding between the lipopeptide and Apo-AI occurs up to a saturation condition, just above equimolar for a 10.7 μM concentration of Apo-AI. A similar value is obtained from circular dichroism spectroscopy, which probes the reduction in α-helical secondary structure of Apo-AI upon addition of C16-GGGRGDS. Electron microscopy images show a persistence of fibrillar structures due to self-assembly of C16-GGGRGDS in mixtures with Apo-AI above the saturation binding condition. A small fraction of spheroidal or possibly "nanodisc" structures was observed. Small-angle X-ray scattering (SAXS) data for Apo-AI can be fitted using a published crystal structure of the Apo-AI dimer. The SAXS data for the lipopeptide/Apo-AI mixtures above the saturation binding conditions can be fitted to the contribution from fibrillar structures coexisting with flat discs corresponding to Apo-AI/lipopeptide aggregates.

Lipopeptide

Isothermal Titration Calorimetry

Small-angle X-ray scattering

10.1039/c4nr05072j

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Shear Alignment of Bola-Amphiphilic Arginine-Coated Peptide Nanotubes

Biomacromolecules (2016)

Ian W. Hamley Samuel Burholt Jessica Hutchinson Valeria Castelletto Emerson Rodrigo da Silva

The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s-1). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rates, very similar to that observed in the bulk using the Couette geometry. A small isotope effect (comparing H2O/D2O solvents) is noted in the CD spectra indicating increased interpeptide hydrogen bonding in D2O, although this does not influence nanotube self-assembly. These results provide new insights into the controlled alignment of peptide nanotubes for future applications.

Small-angle X-ray scattering

10.1021/acs.biomac.6b01425

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Citations (45)

High‐Strength Composite Fibers from Cellulose–Lignin Blends Regenerated from Ionic Liquid Solution

ChemSusChem (2015)

Yibo Ma Shirin Asaadi Leena‐Sisko Johansson Patrik Ahvenainen Mehedi Reza

Abstract Composite fibres that contain cellulose and lignin were produced from ionic liquid solutions by dry‐jet wet spinning. Eucalyptus dissolving pulp and organosolv/kraft lignin blends in different ratios were dissolved in the ionic liquid 1,5‐diazabicyclo[4.3.0]non‐5‐enium acetate to prepare a spinning dope from which composite fibres were spun successfully. The composite fibres had a high strength with slightly decreasing values for fibres with an increasing share of lignin, which is because of the reduction in crystallinity. The total orientation of composite fibres and SEM images show morphological changes caused by the presence of lignin. The hydrophobic contribution of lignin reduced the vapour adsorption in the fibre. Thermogravimetric analysis curves of the composite fibres reveal the positive effect of the lignin on the carbonisation yield. Finally, the composite fibre was found to be a potential raw material for textile manufacturing and as a precursor for carbon fibre production.

Dissolving pulp

Organosolv

Kenaf

10.1002/cssc.201501094

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Citations (107)

Accessibility of Cell Wall Lignin in Solvent Extraction of Ultrathin Spruce Wood Sections

ACS Sustainable Chemistry & Engineering (2013)

Mehedi Reza Leonardo Galvis Rojas Eero Kontturi Tapani Vuorinen Janne Ruokolainen

Wood is a naturally occurring composite, comprising cellulose, hemicellulose, and lignin. The tightly arranged cell wall components make the fibers resistant against chemical and microbial degradation. This natural resisting power of fibers is a technical obstacle during the degradation of cellulose into sugars. Therefore, removal of cell wall lignin is necessary in order to make the cellulose accessible. In this study, ultrathin sections of Norway spruce (Picea abies) branch wood were examined using Raman and transmission electron microscopy (TEM) before and after extracting the sections with 1,4-dioxane without resin embedding in order to study the accessibility of native lignin. The progress of extraction of lignin was followed by measuring its Raman scattering intensity at the ∼1600 cm–1 band. It was found that lignin was extracted not only from the compound middle lamellae but also from other layers of the cell wall. Changes in the contrast of TEM images confirmed a decrease in lignin concentration after solvent extraction. Observed ruptures in the S1 layer indicated that extraction weakened this layer in particular.

Hemicellulose

Middle lamella

10.1021/sc400470m

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Citations (9)

The Effect of Lipidation on the Self-Assembly of the Gut-Derived Peptide Hormone PYY_3–36

Bioconjugate Chemistry (2018)

Jessica Hutchinson Samuel Burholt Ian W. Hamley Anna-Karin Lundbäck Shahid Uddin

Lipidation is a powerful strategy to improve the stability in vivo of peptide drugs. Attachment of a lipid chain to a hydrophilic peptide leads to amphiphilicity and the potential for surfactant-like self-assembly. Here, the self-assembly and conformation of three lipidated derivatives of the gastrointestinal peptide hormone PYY3–36 is examined using a comprehensive range of spectroscopic, scattering, and electron microscopy methods and compared to those of the parent PYY3–36 peptide. The peptides are lipidated at Ser(11), Arg(17), or Arg(23) in the peptide; the former is within the β-turn domain (based on the published solution NMR structure), and the latter two are both within the α-helical domain. We show that it is possible to access a remarkable diversity of nanostructures ranging from micelles to nanotapes and fibrillar hydrogels by control of assembly conditions (concentration, pH, and temperature). All of the lipopeptides self-assemble above a critical aggregation concentration (cac), determined through pyrene fluorescence probe measurements, and they all have predominantly α-helical secondary structure at their native pH. The pH and temperature dependence of the α-helical conformation were probed via circular dichroism spectroscopy experiments. Lipidation was found to provide enhanced stability against changes in temperature and pH. The self-assembled structures were investigated using small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM). Distinct differences in nanostructure were observed for lipidated and unlipidated peptides, also depending on the position of lipidation. Remarkably, micelles containing lipopeptides with α-helical peptide conformation were observed. Gelation was observed at higher concentrations in certain pH intervals for the lipidated peptides, but not for unlipidated PYY3–36. Thus, lipidation, in addition to enhancing stability against pH and temperature variation, also provides a route to prepare PYY peptide hydrogels. These findings provide important insights into the control of PYY3–36 conformation and aggregation by lipidation, relevant to the development of future therapeutics based on this peptide hormone, for example, in treatments for obesity.

Lipid-anchored protein

Small-angle X-ray scattering

10.1021/acs.bioconjchem.8b00286

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Citations (35)

Amphipathic design dictates self-assembly, cytotoxicity and cell uptake of arginine-rich surfactant-like peptides

Journal of Materials Chemistry B (2020)

Lucas R. de Mello Rodrigo Barbosa de Aguiar Renata Yoshiko Yamada Jane Zveiter de Moraes Ian W. Hamley

Amphiphilicity is the most critical parameter in the self-assembly of surfactant-like peptides, regulating the way by which hydrophobic attraction holds peptides together.

10.1039/c9tb02219h

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Citations (40)

Self-assembly of ultra-small micelles from amphiphilic lipopeptoids

Chemical Communications (2017)

King Hang Aaron Lau Valeria Castelletto Thomas Kendall Ján Šefčı́k Ian W. Hamley

Poly(N-substituted glycine) "peptoids" constitute a promising class of peptide-mimetic materials. We introduce the self-assembly of lipopeptoids into spherical micelles ca. 5 nm in diameter as well as larger assemblies by varying the peptoid sequence design. Our results point to design rules for the self-assembly of peptoid nanostructures, enabling the creation of stable, ultra-small peptidomimetic nanospheres.

Peptoid

Peptidomimetic

Sequence (biology)

10.1039/c6cc09888f

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Citations (35)

Self-assembly pathway of peptide nanotubes formed by a glutamatic acid-based bolaamphiphile

Chemical Communications (2015)

Emerson Rodrigo da Silva Wendel A. Alves Valeria Castelletto Mehedi Reza Janne Ruokolainen

The self-assembly of peptide nanotubes formed by anl-glutamic acid-based bolaamphiphile is shown to proceedviaa remarkable mechanism where the peptide conformation changes from β-sheet to unordered.

Glutamic acid

10.1039/c5cc03640b

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Citations (46)

Self-assembly of the anti-fungal polyene amphotericin B into giant helically-twisted nanotapes

Chemical Communications (2015)

Ian W. Hamley Steven Kirkham R.M. Kowalczyk Valeria Castelletto Mehedi Reza

Amphotericin B self-assembles into giant nanotapes with an internal filament structure in pH 12 aqueous solution.

Polyene

10.1039/c5cc08224b

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Citations (2)