LF Structure Research Articles

Effect of pH, protein/polysaccharide ratio and preparation method on the stability of lactoferrin-polysaccharide complexes

In this study, carrageenan (CG), xanthan gum (XG) and locust bean gum (LBG), which can be used in infant formulas in China national standards, were selected to prepare LF-polysaccharide complexes to improve the stability of lactoferrin. The results showed that LF interacted more strongly with polysaccharides and did not affect the LF structure to a large extent when the pH and protein/polysaccharide mass ratio were 7 and 10:1 for LF-CG, 8 and 5:1 for LF-XG, 7 and 15:1 for LF-LBG. The zeta potential and fluorescence intensity of the LF-polysaccharide complexes displayed a decreasing trend with the increase in pH. When pH < 6, LF-CG and LF-XG exhibited precipitation and increased UV absorbance. Complexation between LF and CG/XG mainly attributed to electrostatic interactions, while LF and LBG form complexes based on hydrogen bonding or hydrophobic interactions. This study could provide a reference for the practical application of LF in infant formula.

Effects of ultrasound and thermal treatment on the interaction between hyaluronic acid and lactoferrin: Preparation, structures and functionalities

Complexes of polysaccharides and proteins have superior physicochemical and functional properties compared to single proteins or polysaccharides. In this study, lactoferrin-hyaluronic acid (LF-HA) complexes were prepared by both ultrasonic and thermal treatment. Appropriate preparation conditions, including ultrasonic and thermal treatment conditions, have been established. The complexes formed by different methods were structurally characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis, fourier transform infrared spectroscopy, and circular dichroism spectroscopy. Ultrasound formed non-covalent binding, while thermal treatment generated covalent bonding, altering the structure of LF. The LF-HA complexes showed improved heat stability, foaming stability, emulsifying activity and antioxidant capacity, but deceased foaming ability. Iron binding ability could only be improved by HA through thermal treatment. Moreover, the in vitro digestibility of LF-HA complexes decreased to below 80 % compared to LF.

New Horizons of Covalent Complex of Plant-Derived Recombinant Human Lactoferrin (OsrhLF) Combined with Different Polyphenols: Formation, Physicochemical Properties, and Gastrointestinal Fate.

Four typical dietary polyphenols ((-)-epigallocatechin gallate (EGCG), quinic acid (QA), caffeic acid (CA), and ferulic acid (FA)) were covalently prepared with rice recombinant human lactoferrin (OsrhLF) and bovine lactoferrin (bLF), and their structure and physicochemical properties were investigated, different lycopene emulsions were made by ultrasonic emulsification to analyze gastrointestinal fate. The results indicated that the covalent modification polyphenols changed the secondary/tertiary structure of LF, significantly improving the surface hydrophilicity, thermal stability, and antioxidant activity of LF. Compared with the bLF group, the OsrhLF group was more hydrophilic and the thermal denaturation temperature of the OsrhLF-CA reached 104.4 °C. LF-polyphenol emulsions significantly enhanced the photochemical stability and bioavailability of lycopene and achieved effective encapsulation and protection of lycopene compared to free lycopene, and the OsrhLF-EGCG reached 58.94% lycopene bioavailability. In short, OsrhLF does not differ much from bLF in terms of physicochemical properties and has a strong potential in the field of dietary supplements.

Exploiting Spatial and Angular Correlations With Deep Efficient Transformers for Light Field Image Super-Resolution

Global context information is particularly important for comprehensive scene understanding. It helps clarify local confusions and smooth predictions to achieve fine-grained and coherent results. However, most existing light field processing methods leverage convolution layers to model spatial and angular information. The limited receptive field restricts them to learn long-range dependency in LF structure. In this paper, we propose a novel network based on deep efficient transformers ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.,</i> LF-DET) for LF spatial super-resolution. It develops a spatial-angular separable transformer encoder with two modeling strategies termed as sub-sampling spatial modeling and multi-scale angular modeling for global context interaction. Specifically, the former utilizes a sub-sampling convolution layer to alleviate the problem of huge computational cost when capturing spatial information within each sub-aperture image. In this way, our model can cascade more transformers to continuously enhance feature representation with limited resources. The latter processes multi-scale macro-pixel regions to extract and aggregate angular features focusing on different disparity ranges to well adapt to disparity variations. Besides, we capture strong similarities among surrounding pixels by dynamic positional encodings to fill the gap of transformers that lack of local information interaction. The experimental results on both real-world and synthetic LF datasets confirm our LF-DET achieves a significant performance improvement compared with state-of-the-art methods. Furthermore, our LF-DET shows high robustness to disparity variations through the proposed multi-scale angular modeling.

Lactoferrin: A glycoprotein that plays an active role in human health.

Lactoferrin (Lf), existing widely in human and mammalian milk, is a multifunctional glycoprotein with many functions, such as immune regulation, anti-inflammation, antibacterial, antiviral, and antioxidant. These extensive functions largely attribute to its ability to chelate iron and interfere with the cellular receptors of pathogenic microorganisms and their hosts. Moreover, it is non-toxic and has good compatibility with other supplements. Thus, Lf has been widely used in food nutrition, drug carriers, biotechnology, and feed development. Although Lf has been continuously explored and studied, a more comprehensive and systematic compendium is still required. This review presents the recent advances in the structure and physicochemical properties of Lf as well as clinical studies on human diseases, with the aim of providing a reference for further research of Lf and the development of its related functional products.

Contact Lens Wear Induces Alterations of Lactoferrin Functionality in Human Tears.

The tear film is a complex matrix composed of several molecular classes, from small metal ions to macromolecules. Contact lens (CL) wear can affect the protein homeostasis of the tear film, by accumulating deposits on the CL surface and/or altering their structural and functional properties. This work investigates the effect of CL wear on lactoferrin (Lf), one of the most abundant tear proteins, known as an unspecific biomarker of inflammation. Tears from eight volunteers were collected and analyzed after alternated periods of CL wear and without CL. The experimental approach is to probe Lf into unprocessed human tears by the peculiar fluorescence emission originating from complex formation of Lf with terbium (Tb3+) at the iron-binding sites. The experimental data indicate that CL wear does not significantly affect the total amount of Lf. On the other hand, Lf affinity for Tb3+ is reduced upon CL wear, suggesting relevant changes in Lf structure and possible alterations of protein functionality. Future studies based on this approach will help define CL features (material, lens-care solution, wearing time, etc.) with minimal effects on tear protein activity, in order to obtain more biocompatible and comfortable devices.

Mechanical and energy absorption properties of functionally graded lattice structures based on minimal curved surfaces

Compared with uniform structures, functionally graded lattice structures can control mechanical properties through varying structures and their volume fraction. In this study, a three-period minimal curved surface method was used to generate functional lattice structure with linear or quadratic function (LF or QF) gradient strategy in the forming direction, and the samples were fabricated by selective laser melting (SLM) using the Ti-6Al-4V metal powder. The mechanical properties, deformation behaviors, and energy absorption performance of graded lattice structures, LF, and QF I-Wrapped Package (IW-P) lattice structures were systematically investigated through experiment and finite element analysis (FEA). Based on the experimental and numerical simulation results, the LF lattice structure shows higher elastic modules and yield strength during small strain period. And the merits of performance increased layer-by-layer under large strain. Additionally, the simulation results based on Johnson-Cook and failure model show that this model can reflect structural compression deformation behavior and mechanical performance prediction. Furthermore, the elastic modulus of LF lattice structure is higher than uniform lattice structures by nearly 61.52% under the same lattice volume fraction. Compared to other lattice structures, the LF or QF lattice structures have better support performance under small strain and stronger energy absorption capacity under large strain with the same volume fraction, respectively, which shows superior potential to be applied to manufacture protective devices or vibration damping devices.

Influence of iron binding in the structural stability and cellular internalization of bovine lactoferrin

Lactoferrin (Lf) is an iron-binding glycoprotein and a component of many external secretions with a wide diversity of functions. Structural studies are important to understand the mechanisms employed by Lf to exert so varied functions. Here, we used guanidine hydrochloride and high hydrostatic pressure to cause perturbations in the structure of bovine Lf (bLf) in apo and holo (unsaturated and iron-saturated, respectively) forms, and analyzed conformational changes by intrinsic and extrinsic fluorescence spectroscopy. Our results showed that the iron binding promotes changes on tertiary structure of bLf and increases its structural stability. In addition, we evaluated the effects of bLf structural change on the kinetics of bLf internalization in Vero cells by confocal fluorescence microscopy, and observed that the holo form was faster than the apo form. This finding may indicate that structural changes promoted by iron binding may play a key role in the intracellular traffic of bLf. Altogether, our data improve the comprehension of bLf stability and uptake, adding knowledge to its potential use as a biopharmaceutical.

Spectroscopic and Molecular Modeling Investigation on the Interaction between Folic Acid and Bovine Lactoferrin from Encapsulation Perspectives.

The impact of thermal treatment on the ability of lactoferrin (FL) to bind folic acid (FA) was investigated by employing fluorescence spectroscopy, molecular dynamics and docking tests. The structural and conformational particularities of LF upon heating at 80 °C and 100 °C were first estimated based on the intrinsic fluorescence changes in respect to the native protein. The emission spectra indicated gradual unfolding events accompanied by Trp exposure with increasing temperature. In agreement with the experimental results, molecular modeling investigations showed that the secondary and tertiary structure of LF are slightly affected by the thermal treatment. Some minor unfolding events related particularly to the α-helical regions of LF were observed when the temperature increased to 100 °C. The LF fluorescence quenching upon FA addition indicated that a static mechanism stands behind LF-FA complex formation. Regardless of the simulated temperature, the hydrogen bonds played an important role in regulating the interaction between the protein and ligand. FA binding to LF equilibrated at different temperatures occurred spontaneously, and all complexes displayed good thermodynamic stability. The obtained results support the suitability of LF as biocompatible material, for obtaining micro- and nanoparticles for delivery of dietary supplements or for enhancing the functionality of target delivery systems.

Agreement Mismatch in Partitive Relatives

Agreement Mismatch in Partitive Relatives

Physicochemical properties of lactoferrin under oxidative/halogenative stress

Lactoferrin (Lf) was discovered in the thirties of the twentieth century. Since that time a number of useful properties of Lf (antibacterial, antiviral, pro- and anti-inflammatory, etc.) have been found. That’s why Lf became a promising candidate for pharmaceuticals use. The concentration of Lf strikingly increases in inflammatory focuses due to neutrophil degranulation. At the same time, activated neutrophils starts to generate reactive oxygen and halogen species (ROS and RHS), which leads to the development of oxidative/halogenative stress. In this work, using the fluorescence analysis we found the change of the Lf structure and properties in the inflammation conditions (under oxidatives/halogenative stress). We use two forms of Lf – human Lf, excreted from human milk, and recombinant Lf, excreted from milk of transgenic goats. It was established that the amino acids of Lf (decreasing the number of tryptophanils and primary amines) and protein restructuring undergo modification under the HOCl action, while H2O2 has no influence. These changes in the molecule under the HOCl treatment result in decreasing the iron-binding capacity of Lf.

Variation in Tense and Aspect, and the Temporal Interpretation of Complement Clauses

AbstractIn this paper, we investigate the temporal interpretation of propositional attitude complement clauses in four typologically unrelated languages: Washo (language isolate), Medumba (Niger-Congo), Hausa (Afro-Asiatic), and Samoan (Austronesian). Of these languages, Washo and Medumba are optional-tense languages, while Hausa and Samoan are tenseless. Just like in obligatory-tense languages, we observe variation among these languages when it comes to the availability of so-called simultaneous and backward-shifted readings of complement clauses. For our optional-tense languages, we argue that a Sequence of Tense parameter is active in these languages, just as in obligatory-tense languages. However, for completely tenseless clauses, we need something more. We argue that there is variation in the degree to which languages make recourse to res-movement, or a similar mechanism that manipulates LF structures to derive backward-shifted readings in tenseless complement clauses. We additionally appeal to cross-linguistic variation in the lexical semantics of perfective aspect to derive or block certain readings. The result is that the typological classification of a language as tensed, optionally tensed, or tenseless, does not alone determine the temporal interpretation possibilities for complement clauses. Rather, structural parameters of variation cross-cut these broad classes of languages to deliver the observed cross-linguistic picture.

Conjugation between okra polysaccharide and lactoferrin and its inhibition effect on thermal aggregation of lactoferrin at neutral pH

This study investigated the effect of okra polysaccharides (OP) on the thermal stability of lactoferrin (Lf). Zetasizer and turbidity were used to provide insight about the stability of Lf/OP complexes, structural properties were measured by fluorescence spectroscopy and circular dichroism. The results revealed that OP interacts with Lf through electrostatic attraction. OP prevented heat-induced denaturation and aggregation of Lf molecule while the turbidity and zeta potential decreased with elevated OP concentration. Correspondingly, the average size of Lf aggregates decreased from 470 nm to 180 nm when OP concentration increased from 0.005% to 0.0125%. The internal structure of Lf was significantly influenced by the existence of OP. At low concentrations (<0.0075%), OP resulted in the loss of secondary and tertiary structure of Lf. While at high concentrations (>0.0075%), the secondary and tertiary structure of Lf can be protected after heating. The minimum OP concentration to prevent 0.05% Lf from thermal aggregation was 0.0075%. In conclusion, Lf/OP complexes could enhance the usage of Lf as emulsifying and encapsulation agents in food and pharmaceutical fields.

EGCG Inhibited Lipofuscin Formation Based on Intercepting Amyloidogenic β-Sheet-Rich Structure Conversion.

BackgroundLipofuscin (LF) is formed during lipid peroxidation and sugar glycosylation by carbonyl-amino crosslinks with biomacrolecules, and accumulates slowly within postmitotic cells. The environmental pollution, modern dietary culture and lifestyle changes have been found to be the major sources of reactive carbonyl compounds in vivo. Irreversible carbonyl-amino crosslinks induced by carbonyl stress are essentially toxiferous for aging-related functional losses in modern society. Results show that (-)-epigallocatechin gallate (EGCG), the main polyphenol in green tea, can neutralize the carbonyl-amino cross-linking reaction and inhibit LF formation, but the underlying mechanism is unknown.Methods and ResultsWe explored the mechanism of the neutralization process from protein, cell, and animal levels using spectrofluorometry, infrared spectroscopy, conformation antibodies, and electron microscopy. LF demonstrated an amyloidogenic β-sheet-rich with antiparallel structure, which accelerated the carbonyl-amino crosslinks formation and disrupted proteolysis in both PC12 cells and D-galactose (D-gal)-induced brain aging mice models. Additionally, EGCG effectively inhibited the formation of the amyloidogenic β-sheet-rich structure of LF, and prevented its conversion into toxic and on-pathway aggregation intermediates, thereby cutting off the carbonyl-amino crosslinks.ConclusionsOur study indicated that the amyloidogenic β-sheet structure of LF may be the core driving force for carbonyl-amino crosslinks further formation, which mediates the formation of amyloid fibrils from native state of biomacrolecules. That EGCG exhibits anti-amyloidogenic β-sheet-rich structure properties to prevent the LF formation represents a novel strategy to impede the development of degenerative processes caused by ageing or stress-induced premature senescence in modern environments.

Subject Islands, Reconstruction, and the Flow of the Computation

Recent research has highlighted a remarkable variability in subject island effects. Focusing on intransitive verbs and adjectives, we argue that islandhood is determined at the syntax-semantics interface: subjects qualify as islands when they are interpreted outside the predicative nucleus of the clause, in a categorical LF structure ( Ladusaw 1994 ); they are transparent for extraction when they undergo total reconstruction into the predicative nucleus, giving rise to a thetic structure. The thetic/categorical interpretation depends on various factors (most notably the stage-level versus individual-level nature of the predicate), whose interaction accounts for the observed variability of island effects, as shown by our experimental evidence. The relevance of subject reconstruction need not be stipulated; rather, it follows from a top-down-oriented computation, in which movement dependencies are implemented by a storage-and-retrieval mechanism.

In silico investigation of lactoferrin protein characterizations for the prediction of anti-microbial properties.

Lactoferrin (Lf) is an iron-binding multi-functional glycoprotein which has numerous physiological functions such as iron transportation, anti-microbial activity and immune response. In this study, different in silico approaches were exploited to investigate Lf protein properties in a number of mammalian species. Results showed that the iron-binding site, DNA and RNA-binding sites, signal peptides and transferrin motifs in the Lf structure were highly conserved. Examined sequences showed three conserved motifs which were repeated twice in the Lf structure, demonstrating ancient duplication events in its gene. Also, results suggest that the functional domains in mammalian Lf proteins are Zinc finger, Tubulin/FtsZ, GTPase, α/β hydrolase and Zinc knuckle. The potential site for nucleic acid binding and the major DNA and RNA- binding sites in this protein were found in the lactoferricin (Lfc) fragment. Due to its high positive charge, Lf is able to bind a large number of compounds. Our analysis also revealed that the interactions between Lf and ITLN1, LYZ, CSN2, and CD14 proteins played an important role in the protective activities of Lf. Analysis for the prediction of secondary structures indicated that high amounts of α-helix, β-strand and β-sheet were present in Lf. The high degree of conservation among mammalian Lf proteins indicates that there is a close relationship between these proteins, reflecting their important role.

Syntactic Structures as Descriptions of Sensorimotor Processes

In this paper I propose a hypothesis linking elements of a model of theoretical syntax with neural mechanisms in the domain of sensorimotor processing. The syntactic framework I adopt to express this linking hypothesis is Chomsky’s Minimalism: I propose that the language-independent ’Logical Form’ (LF) of a sentence reporting a concrete episode in the world can be interpreted as a detailed description of the sensorimotor processes involved in apprehending that episode. The hypothesis is motivated by a detailed study of one particular episode, in which an agent grasps a target object. There are striking similarities between the LF structure of transitive sentences describing this episode and the structure of the sensorimotor processes through which it is apprehended by an observer. The neural interpretation of Minimalist LF structure allows it to incorporate insights from empiricist accounts of syntax, relating to sentence processing and to the learning of syntactic constructions.

Modal superlatives: a compositional analysis

Superlative adjectives accompanied by certain modal adjectives like possible (e.g. John bought the largest possible present) are ambiguous between a reading where possible is a regular noun modifier and a reading paraphrasable as ‘as Adj as possible’, called ‘modal superlative reading’. Three interesting restrictions have been observed in the literature. First, possible and some other adjectives ending in -able, but not potential and probable, support the latter reading. Second, when the modal adjective appears postnominally, only the modal superlative reading is available. Third, prenominal possible needs to be in a local configuration to -est in order for the modal superlative reading to arise. Using LF structures independently motivated for degree constructions, the present paper develops a compositional semantic analysis of the modal superlative reading, makes correct new predictions concerning this reading, and—by reconciling previous, opposed syntactic analyses—allows us to derive the three empirical restrictions above. The key innovations are: (i) the previously proposed constituent [possible ▲ellipsis] is interpreted as an amount relative clause, and (ii) this constituent is treated as overtly expressing the comparison class argument of -est.

Recent advances in lactoferrin research and development during the past two years (2007–2009): in lieu of a preface of the special issue lactoferrin

This is a short preface of this Special Issue Lactoferrin, it described the major points of key reporters in 'The 9th International Conference on LF Structure, Function and Applications' in Beijing in late Autumn 2009, and the major articles published in this issue. A panorama and the latest advances of lactoferrin R&D during past two years (2007-2009) was tried to extract.

The scope of -est: evidence from Japanese

It has long been observed that the superlative construction, exemplified by John climbed the highest mountain, has two readings. On the absolute reading, the heights of the relevant mountains in a relevant context are compared; on the comparative reading, relevant climbers’ achievements of mountain climbing are compared (Szabolcsi, Comparative superlatives, MIT Working Papers in Linguistics, 1986). Two theories have been proposed regarding this ambiguity. One theory holds that it results from movement of the superlative morpheme -est (movement theory) (Heim, Association with focus, Doctoral Dissertation, 1985, Notes on superlatives, 1999; Szabolcsi 1986).The other theory holds that the ambiguity is derived by assignment of different values to the context variable C, keeping a single LF structure where -est stays in situ (in-situ theory) (Farkas and Kiss, Nat Lang Linguist Theory 18:417–455, 2000; Sharvit and Stateva, Linguist Philos 25:453–504, 2002). As is pointed out by Heim (1999), a choice between these theories is hard to make based solely on English. Through an investigation of Japanese superlative constructions, this paper argues that, in Japanese at least, a movement theory is required.