Macromolecular Distribution Research Articles

Macromolecular Distribution of a Mixed System on Dodol Ulame by Confocal Laser Staining Microscopy (CLSM)

The aim of this study was to learn more about the macromolecular distribution of the food matrix system in the traditional food Dodol Ulame in order to better understand the interactions between starch, fat and sugar. Microstructural stages included dye selection, staining/coloring, material mixing, and observation. The starch was stained with APTS and the fat with Nile red. The starch was stained using the double staining method with covalent labeling. The samples were analyzed with a Zeiss Inverted LSM 800 AXIO Observer equipped with an AXIO cam 503 color camera and an excitation wavelength of 665 nm and 543 nm. The results indicated that GR was polyhedral. Fat and sugar are evenly distributed in the matrix system. Some of the fat interacts with the starch granules to form a coating that prevents the starch from interacting with the sugar and inhibits the imbibition of water into the starch granules at 50 °C and 70°C. Amylose escapes from the granules and reacts with the sugar solution at a higher temperature of 90 °C, while the free fat acts as a lubricant between the particles. This shows how flour, fat and sugar interact to affect the manufacturing process and the final properties of dodol ulame.

Effect of nanoconfinement on the enzymatic activity of bioactive layer-by-layer assemblies in nanopores

In vivo, enzymatic reactions occur in confined environments. Such conditions can strongly improve enzyme behavior and are therefore interesting to study for further applications in biocatalysis. Here, we report on the influence of nanoconfinement on the catalytic properties of enzyme-based nanotubes, built by the layer-by-layer (LbL) assembly of branched polyethylenimine (bPEI) and glucose oxidase (GOx) in nanoporous polycarbonate membranes (PCm). More precisely, the influence of nanoconfinement on the biocatalytic activity is investigated by varying the number of (bPEI/GOx) bilayers, the concentration of polyelectrolytes (PEs) used for LbL deposition and the pore diameter of the PC membrane. Bicinchoninic acid (BCA) assay is employed to estimate the amount of enzyme loaded in the different LbL assemblies. The enzymatic activity was monitored, and found to depend on the three studied parameters. Typically, it decreases with decreasing pore diameter under high concentration of PEs, which may be attributed to limitations of substrate/product diffusion within the network formed in small pores. However, when lower concentration of PEs is used for the LbL assembly, the assemblies features a different macromolecular distribution and the enzymatic activity becomes optimal for low pore diameters. The results of this study pave the way to a more rational design of enzyme-loaded porous nanostructures for biocatalysis.

FTIR microspectroscopic approach to investigate macromolecular distribution in seed coat cross-sections

Cotton seed coat neps (SCNs) are among the least cleanable impurities in textile industry. SCNs can cause problems by persisting into yarn and fabric, reducing yarn strength, increasing yarn ends-down, and even resulting in uneven dye uptake. The study presented herein investigated the effects of the cultivar on the seed coat contamination using a suite of analytical techniques. The cultivar with more SCNs showed a significantly higher average fiber detachment force, and had a significantly larger number of seeds that required a higher force (> 8 N) for fiber detachment compared to the cultivar with less SCNs. The seeds with a strong fiber-seed attachment could lead to breakage of the seed coat during ginning and produce more SCNs. Fourier transform infrared (FTIR) spectroscopy analysis revealed differences in the biochemical composition in the outer epidermal layers of cotton seeds where the fibers are attached. k-mean cluster analysis of FTIR images and their functional group distribution images revealed that the outer layers and the palisade layer of the seed coats had major differences in molecular concentration and distribution that could contribute to cultivar dependence of SCNs. This study could lead to better understanding of the effects of the cultivar on the generation of SCNs.

Macromolecular composition and substrate range of three marine fungi across major cell types.

Marine fungi exist as three major cell types: unicellular yeasts, filamentous hyphae and zoosporic early-diverging forms, such as the Chytridiomycota (chytrids). To begin to understand the ecological and biogeochemical influence of these cell types within the wider context of other plankton groups, cell size and macromolecular composition must be assessed across all three cell types. Using a mass-balance approach to culture, we describe quantitative differences in substrate uptake and subsequent macromolecular distribution in three model marine fungi: the yeast Metschnikowia zobellii, the filamentous Epicoccum nigrum and chytrid Rhizophydium littoreum. We compared these model cell types with select oleaginous phytoplankton of specific biotechnological interest through metanalysis. We hypothesise that fungal cell types will maintain a significantly different macromolecular composition to one another and further represent an alternative grazing material to bacterioplankton and phytoplankton for higher trophic levels. Assessment of carbon substrate range and utilisation using phenotype arrays suggests that marine fungi have a wide substrate range. Fungi also process organic matter to an elevated-lipid macromolecular composition with reduced-protein content. Because of their size and increased lipid composition compared to other plankton groups, we propose that fungi represent a compositionally distinct, energy-rich grazing resource in marine ecosystems. We propose that marine fungi could act as vectors of organic matter transfer across trophic boundaries, and supplement our existing understanding of the microbial loop and carbon transfer in marine ecosystems.

Statistical correlation between waste macromolecular composition and anaerobic fermentation temperature for specific short-chain fatty acid production

To properly exploit short-chain fatty acids (SCFAs) in the chemical industry, it is of foremost importance to ensure stable SCFA profile production via anaerobic fermentation (AF). The different macromolecular distribution of food wastes (FWs) used as feedstock might be crucial for process outcome. Targeting at a specific SCFAs profile and yield, this study explored the statistical correlation between the macromolecular composition of FWs and the produced SCFAs in batch-AFs at 25 °C and 55 °C. Principal Component Analysis (PCA) revealed that the carbohydrates fraction was directly related with butyric acid accumulation, regardless of process temperature. Nevertheless, operational temperature resulted in a pH change, which ultimately affected the process fate. PCA of 25 °C-batch-AF showed a positive correlation between high carbohydrate content and longer-chain acids accumulation. By contrast, 55 °C-AF resulted in higher product specificity than at 25 °C, mainly due to butyrate-type fermentation of carbohydrates. Batch results were further validated in a semicontinuous reactor. Prevailing SCFAs and high bioconversion efficiencies relied on 3 main FWs characteristics: high carbohydrate content (>77% w/w), high carbohydrate/protein ratio (≥10) and high soluble organic matter content. Results obtained herein allowed predicting a specific SCFAs profile based on FWs composition, which is relevant for setting proper downstream technologies.

Chemometric modeling of palate fullness in lager beers

Palate fullness and mouthfeel of beer are key attributes of sensory beer quality. Non-volatile substances and molar mass fractions influence sensory perceptions of palate fullness and mouthfeel. However, systematic correlations between sensory attributes and native beer compounds have not been evaluated within the concentration range found in lager beer. This article reports a chemometric analysis of 41 lager beers by evaluating analytical data of beer compositions, palate fullness, and mouthfeel descriptors. AF4-MALS-dRI indicated high variability in the macromolecular compositions of classical lager beers. Screened beers were clustered into groups differing significantly in palate fullness intensity and macromolecular distribution. Significant correlations were found between palate fullness and macromolecular fractions and beer composition parameters: original gravity, viscosity, indices of macromolecular distribution, total nitrogen (p < 0.001), and β-glucan (p < 0.01). Thus, a model was built using partial least square regression (PLS) analysis to predict the palate fullness intensity in beers (R2C = 0.7993). This model can be used as a guideline by brewers to control palate fullness and mouthfeel.

Influence of malt modification and the corresponding macromolecular profile on palate fullness in cereal-based beverages

The sensory attribute palate fullness of cereal-based beverages was shown to be affected by polymeric compounds and their macromolecular profile. During malting, the enzymatic degradation of polymers is technologically controlled by the malting parameters, namely the degree of steeping, germination time, and germination temperature. The macromolecular profile of a fermented cereal-based beverage consists of non-fermentable substance classes. Therefore, the macromolecular composition of a final beverage is originally dominated by the raw material, if conventional production methods are used. We investigated the influence of different cytolytic and proteolytic malt modifications on the macromolecular profile of lactic acid-fermented cereal-based beverages (a strain was selected that did not produce exopolysaccharides) and their resultant effect on the sensory perception of the attributes of palate fullness and mouthfeel. Asymmetrical-flow field-flow fractionation coupled with multi-angle light-scattering detection and refractive index detection is an analytical tool for macromolecular characterization to indicate differences in the macromolecular profile, molar mass, and molar mass distribution. The beverages produced using different modified malts demonstrated a considerable variation in their final composition, particularly in the composition of their macromolecular compounds. A higher level of malt modification led to a decrease in the high-molar-mass fraction and a consequent shift toward fractions with a lower molar mass. Malts produced from barley with increased crude protein contents resulted in a greater range within the macromolecular profile. The variation of germination time significantly influenced the number average molar mass, the total refractive index detection (dRI) peak area, and the high-molar-mass fraction, which contained cell wall polysaccharides (60–1200 kDa). The perception of the intensity of palate fullness was significantly correlated with specific macromolecular fractions, which were influenced by the malting parameter degree of steeping and the resultant modification. The perception of the mouthfeel descriptor watery varied significantly for different crude protein contents. Our results are beneficial for a targeted design of beverage composition based on the macromolecular profile by an improved selection of raw materials and malting technology.

Soil Type and Cyanobacteria Species Influence the Macromolecular and Chemical Characteristics of the Polysaccharidic Matrix in Induced Biocrusts

Inoculation of soils with cyanobacteria is proposed as a sustainable biotechnological technique for restoration of degraded areas in drylands due to the important role that cyanobacteria and their exopolysaccharides (EPS) play in the environment. So far, few studies have analyzed the macromolecular and chemical characteristics of the polysaccharidic matrix in induced cyanobacterial biocrusts and the scarce existing studies have mainly focused on sandy soil textures. However, the characteristics of the cyanobacterial polysaccharidic matrix may greatly depend on soil type. The objective of this study was to examine the macromolecular distribution and monosaccharidic composition of the polysaccharidic matrix induced by inoculation of two cyanobacterial species common in arid environments, Phormidium ambiguum (non N-fixing) and Scytonema javanicum (N-fixing) in different soil types. S. javanicum promoted a higher release in the soil of the more soluble and less condensed EPS fraction (i.e., the loosely bound EPS fraction, LB-EPS), while P. ambiguum showed a higher release of the less soluble and more condensed EPS fraction (i.e., the tightly bound EPS fraction, TB-EPS). LB-EPSs were mainly composed of low MW molecules (< 50 kDa), while TB-EPSs were mainly composed of high MW molecules (1100–2000 kDa). The two EPS fractions showed a complex monosaccharidic composition (from 11 to 12 different types of monosaccharides), with glucose as the most abundant monosaccharide, in particular in the poorer soils characterized by lower organic C contents. In more C-rich soils, high abundances of galactose, mannose, and xylose were also found. Low abundance of uronic acids and hydrophobic monosaccharides, such as fucose and rhamnose, was found in the EPS extracted from the inoculated soils. Our results point to the influence of soil type on the macromolecular distribution and monosaccharide composition of the polysaccharidic matrix in induced biocrusts, which is likely to affect biocrust development and their role in soil structure and nutrient cycling in restored dryland soils.

Macromolecular Distribution Volume in Human Ovarian and Endometrial Cancer

Elements of the extracellular matrix (ECM), notably collagen and glucosaminoglycans, will restrict part of the space available for soluble macromolecules because the molecules cannot occupy the same space. This phenomenon may influence macromolecular drug uptake. To study the influence of steric and charge effects of the ECM on the distribution volumes of macromolecules in human healthy and malignant gynecologic tissues we used as probes 15 abundant plasma proteins quantified by high-resolution mass spectrometry. The available distribution volume (VA) of albumin was increased in ovarian carcinoma compared with healthy ovarian tissue. Furthermore, VA of plasma proteins between 40 and 190 kDa decreased with size for endometrial carcinoma and healthy ovarian tissue, but was independent of molecular weight for the ovarian carcinomas. An effect of charge on distribution volume was only found in healthy ovaries, which had lower hydration and high collagen content, indicating that a condensed interstitium increases the influence of negative charges. A number of earlier suggested biomarker candidates were detected in increased amounts in malignant tissue, showing that interstitial fluid, even when unfractionated, can be a valuable source for tissue-specific proteins. We demonstrate that the distribution of abundant plasma proteins in the interstitium can be elucidated by mass spectrometry methods and depends markedly on hydration and ECM structure. Our data can be used in modeling of drug uptake, and give indications on ECM components to be targeted to increase the uptake of macromolecular substances.

Enhanced methane production of Chlorella vulgaris and Chlamydomonas reinhardtii by hydrolytic enzymes addition

The effect of enzymatic hydrolysis on microalgae organic matter solubilisation and methane production was investigated in this study. Even though both biomasses, Chlamydomonas reinhardtii and Chlorella vulgaris, exhibited similar macromolecular distribution, their cell wall composition provided different behaviors. The addition of carbohydrolase (Viscozyme) and protease (Alcalase) resulted in high carbohydrates and protein solubilisation on both biomasses (86–96%). Despite the high carbohydrate solubilisation with the carbohydrolase, methane production was enhanced by 14% for C. vulgaris, while hydrolyzed C. reinhardtii did not show any improvement. The addition of protease to C. reinhardtii increased methane production by 1.17-fold. The low enhancement achieved together with the inherent high biodegradability of this biomass would not justify the cost associated to the enzyme addition. On the other hand, C. vulgaris hydrolyzed with the protease resulted in 86% anaerobic biodegradability compared to 54% of the raw biomass. Therefore, the application of protease prior anaerobic digestion of C. vulgaris could be a promising approach to decrease the energetic input required for cell wall disruption.

Impact of microalgae characteristics on their conversion to biofuel. Part II: Focus on biomethane production

AbstractAmong biofuel production processes using microalgal biomass, biogas generation seems to be the least complex. This review summarizes information regarding anaerobic digestion of different microalgae species. Various operational parameters and microalgae characteristics (macromolecular distribution and cell wall) are reviewed in the light of their effects on methane production. Additionally, the enhancement of methane production rates achievable by applying biomass pre‐treatments and codigestion of substrates is also reported. The review finally covers the so‐claimed similarities of microalgal biomass and activated sludge as a substrate for anaerobic digestion. © 2011 Society of Chemical Industry and John Wiley &amp; Sons Ltd

Asymmetric Response of Carbon Metabolism at High and Low Salt Stress in Vibrio sp. DSM14379

Energy redistribution between growth and maintenance in salt-stressed cells is especially important for bacteria living in estuarine environments. In this study, Gram-negative bacterium Vibrio sp. DSM14379, isolated from the estuarine waters of the northern Adriatic Sea, was grown aerobically in a peptone-yeast extract medium with different salt concentrations (ranging from 0.3% to 10% (w/v) NaCl). Carbon flux through the central metabolic pathways was determined at low and high salt concentrations. At low salt concentrations, total endogenous respiration, dehydrogenase activity, and net intracellular adenosine triphosphate (ATP) concentration significantly increased, the phosphofructokinase and pyruvate kinase activity decreased, whereas glucose-6-phosphate dehydrogenase activity remained unchanged. The carrying capacity of bacterial culture decreased dramatically, indicating a severe metabolic imbalance at low salt concentrations. At high salt concentrations, carrying capacity decreased gradually. There was a large increase in glucose-6-phosphate dehydrogenase activity, which correlated with a 10-fold increase in concentration of osmoprotectant L-proline. There was no significant change of net intracellular ATP concentration, phosphofructokinase, or pyruvate kinase activity. The results indicate that Vibrio sp. DSM14379 central metabolic pathways respond to low and high salt concentrations asymmetrically; cells are better adapted to high salt concentrations. In addition, cells in the stationary phase can tolerate induced salt stress without a significant change in dehydrogenase activity or endogenous respiration for at least 1 h, but need to alter their macromolecular composition and carbon flux distribution for long-term survival.

Macromolecular profiling of apoptosis via a multiplex biophotonic platform

Traditional fluorescence microscopy is limited to visualizing labeled molecules and does not fully answer questions about molecular composition or cell/tissue organization. As all cells are composed of thousands of individual types of macromolecule, an understanding of the structural organization and specific mutual interactions between macromolecules is important for development in the biomedical sciences and applied medicine. Major vital cellular functions and substructures—such as cytoplasmic organelles—rely upon interactions between proteins, nucleic acids, saccharides, and lipids. Thus, for a comprehensive understanding of how the cell is organized and its function on a molecular level, knowledge of all types of macromolecular distribution, spatial dynamics, and transformations is required. A multiplex biophotonic platform, recently developed by our group, allows for the quantitative characterization and realtime monitoring of local molecular environments in the structural domains of live cells. We combined coherent anti-Stokes Raman scattering (CARS) and two-photon excited fluorescence (TPEF) nonlinear optical imaging with fluorescence recovery after photobleaching (FRAP) and Raman spectroscopy to study the process of apoptosis, a programmed cell death essential for physiological regulation and elimination of genetic disorders.1 While the ability to combine nonlinear imaging has been demonstrated before in the pioneering CARS work of the Sunney Xie group at Harvard University,2 we applied the CARS/TPEF combination for quasi-synchronous multiplex imaging (multiple pictures in one scan) of proteins, lipids, DNA, and RNA during apoptosis.1 Proteins and lipids were distinguished by CARS, while acridine orange-labeled nucleic acids by TPEF responded in green and red spectral channels. CARS/TPEF Figure 1. The distribution of proteins, lipids, DNA, and RNA in HeLa cells during apoptotic development as visualized using multimodal coherent anti-Stokes Raman scattering (CARS) and two-photon excitedfluorescence (TPEF) imaging over 24h. Proteins (red) and lipids (grey) were observed in the CARS mode at the characteristic vibrations of 2928cm 1 and 2890cm 1, respectively. Nucleic acids, stained with acridine orange, were acquired in the red (RNA= green) and green (DNA= blue) fluorescence channels in TPEF mode.

Abdominal Obesity: Role in the Pathophysiology of Metabolic Disease and Cardiovascular Risk

Visceral adiposity has been identified as an independent risk factor for cardiovascular disease and the so-called metabolic syndrome. The canine obesity model closely recapitulates the correlation between human visceral adiposity and insulin resistance. A recent canine study indicates that insulin expands the volume of distribution associated with skeletal muscle, and that its ability to enhance macromolecular distribution within this space is blunted in the fat-fed obese canine model. Our canine study supports the portal theory of insulin resistance, in which free fatty acids (FFAs) from visceral fat directly enter the liver and have a detrimental effect on insulin action. The role of adipokines in this condition remains less clear. Sympathetic nervous system hyperactivity in obesity may also contribute to excessive FFA release, hypertension, and insulin resistance. Pathologies interrelated with insulin resistance include β-cell hypersecretion, reduced insulin clearance, and resultant hyperinsulinemia. An observed nocturnal increase in plasma FFA levels may account for both insulin resistance and compensatory hyperinsulinemia and warrants further investigation. The elucidation of these interrelated pathologies may help reveal points where medical intervention can reduce metabolic disease.

Atomic force microscopy applied to study macromolecular content of embedded biological material

We demonstrate that atomic force microscopy represents a powerful tool for the estimation of structural preservation of biological samples embedded in epoxy resin, in terms of their macromolecular distribution and architecture. The comparison of atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of a biosample ( Caenorhabditis elegans) prepared following to different types of freeze-substitution protocols (conventional OsO 4 fixation, epoxy fixation) led to the conclusion that high TEM stainability of the sample results from a low macromolecular density of the cellular matrix. We propose a novel procedure aimed to obtain AFM and TEM images of the same particular organelle, which strongly facilitates AFM image interpretation and reveals new ultrastructural aspects (mainly protein arrangement) of a biosample in addition to TEM data.

The interstitial distribution of macromolecules in rat tumours is influenced by the negatively charged matrix components

Knowledge of macromolecular distribution volumes is essential in understanding fluid transport within normal and pathological tissues. In this study in vivo we determined the distribution volumes of several macromolecules, including one monoclonal antibody, in tumours and tested whether charges associated with the tumour extracellular matrix influence their available volumes. Steady state levels of the monoclonal antibody trastuzumab (Herceptin) (pI = 9.2), IgG (pI = 7.6) as well as native (pI = 5.0) and cationized albumin (pI = 7.6) were established in rats bearing dimethylbenzanthracene (DMBA)-induced mammary tumours by continuous infusion using osmotic minipumps. After a 5-7 day infusion period, the rats were nephrectomized and the extracellular volume was determined with 51Cr-labelled EDTA. Plasma volumes were measured with 125I-labelled human serum albumin or rat IgM in a separate series. Steady state concentrations of probes were determined in the interstitial fluid that was isolated by centrifugation from tumours or by post mortem wick implantation in the back skin. Calculations were made for interstitial fluid volume (Vi), along with the available (Va/Vi) and excluded (Ve/Vi) relative interstitial volume fractions. The Ve/Vi for the positively charged trastuzumab in tumours averaged 0.29 +/- 0.03 (n = 16), a value which was significantly lower than the corresponding one for IgG of 0.36 +/- 0.02 (n = 16). Native albumin was excluded from 38% of the tumour interstitial fluid, whereas cationization of albumin reduced the excluded volume by approximately 50%. Our experiments suggest that the tumour interstitium acts as a negatively charged matrix and is an important factor in determining the macromolecular distribution volume.

Coupled macromolecular transport and gel mechanics: Poroviscoelastic approach

AbstractDesigning drug delivery devices or drug delivery protocols poses problems because they are considered to operate in a mechanically static environment. It should consider, however, transport processes in these cases occur in a mechanically dynamic environment since mechanical stimuli may strongly influence transport within soft hydrated materials. A general framework combines fluid and macromolecular transport with the mechanics of hydrated polymer gels or tissue. As an example, the model equations have been created for a spherical geometry to describe the distribution of macromolecules within the gel resulting from a constant pressure or a constant flow infusion source. The model describes the overall average profiles of the interstitial fluid pressure, velocity and solid matrix dilatation, displacement, and stress, as well as macromolecular distribution. The basic theory provides new insight into understanding the transport of macromolecules within mechanically stimulated polymeric gels and tissues and, therefore, represents a valuable tool for designing and engineering novel drug delivery systems, as well as optimization of drug delivery protocols to be used in detection and treatments.

The steady/pulsatile flow and macromolecular transport in T-bifurcation blood vessels

A numerical analysis of the steady and pulsatile, macromolecular (such as low density lipopotein (LDL), Albumin) transport in T-bifurcation was proposed. The influence of Reynolds number and mass flow ratio etc. parameters on the velocity field and mass transport were calculated. The computational results predict that the blood flow factors affect the macromolecular distribution and the transport across the wall, it shows that hemodynamic play an important role in the process of atherosclerosis. The LDL and Albumin concentration on the wall varies most greatly in flow bifurcation area where the wall shear stress varies greatly at the branching vessel and the atherosclerosis often appears there.

Successful and safe perfusion of the primate brainstem: in vivo magnetic resonance imaging of macromolecular distribution during infusion.

Intrinsic disease processes of the brainstem (gliomas, neurodegenerative disease, and others) have remained difficult or impossible to treat effectively because of limited drug penetration across the blood-brainstem barrier with conventional delivery methods. The authors used convection-enhanced delivery (CED) of a macromolecular tracer visible on magnetic resonance (MR) imaging to examine the utility of CED for safe perfusion of the brainstem. Three primates (Macaca mulatta) underwent CED of various volumes of infusion ([Vis]; 85, 110, and 120 microl) of Gd-bound albumin (72 kD) in the pontine region of the brainstem during serial MR imaging. Infusate volume of distribution (Vd), homogeneity, and anatomical distribution were visualized and quantified using MR imaging. Neurological function was observed and recorded up to 35 days postinfusion. Histological analysis was performed in all animals. Large regions of the pons and midbrain were successfully and safely perfused with the macromolecular protein. The Vd was linearly proportional to the Vi (R2 = 0.94), with a Vd/Vi ratio of 8.7 +/- 1.2 (mean +/- standard deviation). Furthermore, the concentration across the perfused region was homogeneous. The Vd increased slightly at 24 hours after completion of the infusion, and remained larger until the intensity of infusion faded (by Day 7). No animal exhibited a neurological deficit after infusion. Histological analysis revealed normal tissue architecture and minimal gliosis that was limited to the region immediately surrounding the cannula track. First, CED can be used to perfuse the brainstem safely and effectively with macromolecules. Second, a large-molecular-weight imaging tracer can be used successfully to deliver, monitor in vivo, and control the distribution of small- and large-molecular-weight putative therapeutic agents for treatment of intrinsic brainstem processes.

Structure of the macromolecular solutions that generate crystals

Biomolecular interactions in solution include a variety of effects: hard sphere, electrostatic, van der Waals, hydrophobic, etc. The corresponding interaction potentials govern the macromolecular distribution in solution, the shapes of the phase diagrams and the crystallization process. Different techniques: small angle X-ray scattering (SAXS), light scattering, osmotic pressure, can be used to characterize these potentials. Here, SAXS was the tool of choice to follow the changes induced by the crystallizing agents in different physicochemical conditions. Moreover, the coupling of SAXS (experimental structure factors) and numerical simulations derived from statistical mechanics (calculated structure factors) allowed us to determine the best fit parameters of the relevant potentials. Several protein model systems have now been investigated, with different isoelectric points, sizes and compactness. After the studies performed on lysozyme, and on aspartate transcarbamylase (ATCase), we proceeded with lens gamma- and alpha-crystallins and with urate oxidase. We can now draw the following picture of the relevant potentials. With low molecular weight proteins, a coulombic, pH dependent, repulsive potential and a short range (a few Å), possibly van der Waals, attraction are sufficient to account for the behavior observed at low ionic strength. At higher ionic strength, the salt specific effects that follow the (direct or reverse) order of the Hofmeister series, correspond to an additional short range salt specific attraction. With increasing protein size, the van der Waals contribution becomes negligible. The addition of polymers like polyethylene glycol (PEG) induces a depletion mechanism, which is equivalent to a protein–protein attraction. Crystallization definitively appears to be under control of sufficiently strong and short range (a few Å) attractions, which means that, despite the diversity of protein sequences, it is possible to define a range of physicochemical conditions that may generate crystals. Yet, if salt addition appears to be sufficient to provide such conditions with small compact proteins, additives like PEG seem to be required at higher molecular weights. The success, of course, will also rely upon the protein purity and stability.