High resolution imaging of soft alginate hydrogels by atomic force microscopy.

This work explores the largely unknown surface microstructure and elastic modulus of soft calcium-alginate hydrogels (E = 100-4500 Pa) in their hydrated state by atomic force microscopy (AFM) in quantitative imaging mode. Alginate concentration influenced the surface topography with surface roughness measured to be 101 ± 6 nm and 57 ± 1 nm for 0.5 and 2.

Elucidating bacterial adhesion to mucosal surface by an original AFM approach.

Background: Fish skin represents an ancient vertebrate mucosal surface, sharing characteristics with other mucosal surfaces including those of the intestine. The skin mucosa is continuously exposed to microbes in the surrounding water and is therefore important in the first line defense against environmental pathogens by preventing bacteria from accessing the underlying surfaces. Understanding the microbe-host interactions at the fish skin mucosa is highly relevant in order to understand and control infection, commensalism, colonization, persistence, infection, and disease.

A Titratable Cell Lysis-on-Demand System for Droplet-Compartmentalized Ultrahigh-Throughput Screening in Functional Metagenomics and Directed Evolution.

Water-in-oil emulsion droplets are an attractive format for ultrahigh-throughput screening in functional metagenomics and directed evolution applications that allow libraries with more than 10 members to be characterized in a day. Single library members are compartmentalized in droplets that are generated in microfluidic devices and tested for the presence of target biocatalysts. The target proteins can be produced intracellularly, for example, in bacterial hosts in-droplet cell lysis is therefore necessary to allow the enzymes to encounter the substrate to initiate an activity assay.

Insights into the roles of charged residues in substrate binding and mode of action of mannuronan C-5 epimerase AlgE4.

Mannuronan C-5 epimerases catalyze the epimerization of monomer residues in the polysaccharide alginate, changing the physical properties of the biopolymer. The enzymes are utilized to tailor alginate to numerous biological functions by alginate-producing organisms. The underlying molecular mechanism that control the processive movement of the epimerase along the substrate chain is still elusive.

Exploring the effects of approach velocity on depletion force and coalescence in oil-in-water emulsions.

An emulsion is a thermodynamically unstable system consisting of at least two immiscible liquid phases, one of which is dispersed in the other in the form of droplets of varying size. Most studies on emulsions have focused on the behaviour of emulsion droplets with diameter from ∼50 μm and upwards. However, the properties of smaller droplets may be highly relevant in order to understand the behaviour of emulsions, including their performance in numerous applications within the fields of food, industry, and medical science.

Effect of design geometry, exposure energy, cytophilic molecules, cell type and load in fabrication of single-cell arrays using micro-contact printing.

In this study a range of factors influencing the fabrication of single-cell arrays (SCAs) are identified and investigated. Micro-contact printing was used to introduce spots coated with polyethyleneimine or Matrigel on glass surfaces pre-coated with polyethylene glycol. Unmodified E.

Tn and STn are members of a family of carbohydrate tumor antigens that possess carbohydrate-carbohydrate interactions.

The mucin-type O-glycome in cancer aberrantly expresses the truncated glycans Tn (GalNAcα1-Ser/Thr) and STn (Neu5Acα2,6GalNAcα1-Ser/Thr). However, the role of Tn and STn in cancer and other diseases is not well understood. Our recent discovery of the self-binding properties (carbohydrate-carbohydrate interactions, CCIs) of Tn (Tn-Tn) and STn (STn-STn) provides a model for their possible roles in cellular transformation.

Correction: Interactions between the breast cancer-associated MUC1 mucins and C-type lectin characterized by optical tweezers.

[This corrects the article DOI: 10.1371/journal.pone.

Interactions between the breast cancer-associated MUC1 mucins and C-type lectin characterized by optical tweezers.

Carbohydrate-protein interactions govern many crucial processes in biological systems including cell recognition events. We have used the sensitive force probe optical tweezers to quantify the interactions occurring between MGL lectins and MUC1 carrying the cancer-associated glycan antigens mucins Tn and STn. Unbinding forces of 7.

Interactions of mucins with the Tn or Sialyl Tn cancer antigens including MUC1 are due to GalNAc-GalNAc interactions.

The molecular mechanism(s) underlying the enhanced self-interactions of mucins possessing the Tn (GalNAcα1-Ser/Thr) or STn (NeuNAcα2-6GalNAcα1-Ser/Thr) cancer markers were investigated using optical tweezers (OT). The mucins examined included modified porcine submaxillary mucin containing the Tn epitope (Tn-PSM), ovine submaxillary mucin with the STn epitope (STn-OSM), and recombinant MUC1 analogs with either the Tn and STn epitope. OT experiments in which the mucins were immobilized onto polystyrene beads revealed identical self-interaction characteristics for all mucins.

Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy.

Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g.

The Design of Simple Bacterial Microarrays: Development towards Immobilizing Single Living Bacteria on Predefined Micro-Sized Spots on Patterned Surfaces.

In this paper we demonstrate a procedure for preparing bacterial arrays that is fast, easy, and applicable in a standard molecular biology laboratory. Microcontact printing is used to deposit chemicals promoting bacterial adherence in predefined positions on glass surfaces coated with polymers known for their resistance to bacterial adhesion. Highly ordered arrays of immobilized bacteria were obtained using microcontact printed islands of polydopamine (PD) on glass surfaces coated with the antiadhesive polymer polyethylene glycol (PEG).

The Breast Cancer-Associated Glycoforms of MUC1, MUC1-Tn and sialyl-Tn, Are Expressed in COSMC Wild-Type Cells and Bind the C-Type Lectin MGL.

Aberrant glycosylation occurs in the majority of human cancers and changes in mucin-type O-glycosylation are key events that play a role in the induction of invasion and metastases. These changes generate novel cancer-specific glyco-antigens that can interact with cells of the immune system through carbohydrate binding lectins. Two glyco-epitopes that are found expressed by many carcinomas are Tn (GalNAc-Ser/Thr) and STn (NeuAcα2,6GalNAc-Ser/Thr).

Single molecule study of heterotypic interactions between mucins possessing the Tn cancer antigen.

Mucins are linear, heavily O-glycosylated proteins with physiological roles that include cell signaling, cell adhesion, inflammation, immune response and tumorgenesis. Cancer-associated mucins often differ from normal mucins by presenting truncated carbohydrate chains. Characterization of the binding properties of mucins with truncated carbohydrate side chains could thus prove relevant for understanding their role in cancer mechanisms such as metastasis and recognition by the immune system.

Structure-function relationships in glycopolymers: effects of residue sequences, duplex, and triplex organization.

The importance of residue sequence and duplex and triplex structures as basis for establishing molecular understanding of the structure-function relationships within glycopolymers is highlighted. The copolysaccharide alginate is the selected example for elucidating effects of residue sequence on functional properties like ionotropic gelation. Xanthan and comblike branched β-D-glucans are used as examples of impact of duplex and triplex organization on global conformation and functional properties.

Higher order structures of a bioactive, water-soluble (1→3)-β-D-glucan derived from Saccharomyces cerevisiae.

Water-soluble (1→3)-β-D-glucans with 1,6-linked branches (SBG), originally isolated from the cell walls of Saccharomyces cerevisiae and partially depolymerised to a weight average degree of polymerisation (DP(w)) in the range 120-160 for optimal performance in wound healing applications, were studied by dynamic light scattering (DLS), SEC MALLS and AFM. Results indicate that dilute aqueous SBG solutions (1 μg/ml to 3 mg/ml) contain higher order structures with a very wide size distribution in water (10-500 nm), corresponding to a mixture of single chains, multi-chain aggregates including triple-stranded motifs, and particulate materials. The latter were enriched in longer chains compared to non-particulate fractions.

Enhanced self-association of mucins possessing the T and Tn carbohydrate cancer antigens at the single-molecule level.

Mucins are linear O-glycosylated glycoproteins involved in inflammation, cell adhesion, and tumorigenesis. Cancer-associated mucins often possess increased expression of the T (Galβ1,3GalNAcαThr/Ser) and Tn (GalNAcαThr/Ser) cancer antigens, which are diagnostic markers for several cancers, including colon cancer. We have used AFM based single-molecule forced unbinding under near physiological conditions to investigate the self-interactions between porcine submaxillary mucin (PSM) as well as between PSM analogs possessing various carbohydrates including the T- and Tn-antigen.

Responsive hydrogels for label-free signal transduction within biosensors.

Hydrogels have found wide application in biosensors due to their versatile nature. This family of materials is applied in biosensing either to increase the loading capacity compared to two-dimensional surfaces, or to support biospecific hydrogel swelling occurring subsequent to specific recognition of an analyte. This review focuses on various principles underpinning the design of biospecific hydrogels acting through various molecular mechanisms in transducing the recognition event of label-free analytes.

Single molecular pair interactions between hydrophobically modified hydroxyethyl cellulose and amylose determined by dynamic force spectroscopy.

Interactions among HMHEC (hydrophobically modified hydroxyethyl cellulose) and between HMHEC and amylose were investigated by means of dynamic force spectroscopy of single molecular pairs. The technique was realized using a scanning probe based platform, and the molecular pair interactions were investigated in aqueous solutions over a range of force loading rates. Both hydrophobic interactions among hydrophobe C(16) alkyl side chains in HMHEC and association between these hydrophobes in HMHEC and amylose showed a stretching type peak.

Single-molecule pair studies of the interactions of the alpha-GalNAc (Tn-antigen) form of porcine submaxillary mucin with soybean agglutinin.

Mucins form a group of heavily O-glycosylated biologically important glycoproteins that are involved in a variety of biological functions, including modulating immune response, inflammation, and adhesion. Mucins are also involved in cancer and metastasis and often express diagnostic cancer antigens. Recently, a modified porcine submaxillary mucin (Tn-PSM) containing GalNAcalpha1-O-Ser/Thr residues was shown to bind to soybean agglutinin (SBA) with approximately 10(6)-fold enhanced affinity relative to GalNAcalpha1-O-Ser, the pancarcinoma carbohydrate antigen.

The fluid phase of morsellized bone: characterization of viscosity and chemical composition.

Morsellized bone is widely used in orthopaedics to fill skeletal defects. The material behaviour is highly time-dependent, due to the liquid consisting of fat and water present in the impacted graft layer. In this study this fluid was characterized with respect to viscosity and chemical composition.

Higher order structure of (1,3)-beta-D-glucans and its influence on their biological activities and complexation abilities.

(1,3)-beta-D-Glucans form a group of biologically active biopolymers that exist in different structural organizations depending on the environmental conditions. The biological effect of (1,3)-beta-D-glucans is a core issue stimulating large research efforts of the molecular properties and their consequences for action as biological response modifiers. The fascination for these molecules increased further following the finding of their ability to form complexes of defined geometry with a number of structures, ranging from linear architectures as polymers or carbon nanotubes, to globular structures as gold particles or dye molecules.

Potentiation of histamine release by Microfungal (1-->3)- and (1-->6)-beta-D-glucans.

(1-->3)-beta-D-Glucans, a cell wall component in most microfungi, are suggested to play a role in the development of respiratory and general symptoms in organic dust-related diseases. The mechanisms by which they induce these effects are, however, not clear. In the present study, mediator release and its potentiation by the (1-->3)-beta-D-glucan as well as by the (1-->6)-beta-D-glucan found in yeast and other fungi were therefore examined.

Influence of oligoguluronates on alginate gelation, kinetics, and polymer organization.

Structural polysaccharides of the alginate family form gels in aqueous Ca2+-containing solutions by lateral association of chain segments. The effect of adding oligomers of alpha-l-guluronic acid (G blocks) to gelling solutions of alginate was investigated using rheology and atomic force microscopy (AFM). Ca-alginate gels were prepared by in situ release of Ca2+.