Structural Characteristics, Operational Methods, and Separation Applications of Dextran Gels

Dextran gel is one of the most classical hydrophilic polysaccharide matrices used in gel filtration and molecular-sieving separation. Its application value lies not only in routine desalting and buffer exchange, but also in the relatively clear correspondence among crosslinked structure, swelling behavior, and pore-size distribution, which enables structural differences in the material to be translated into reproducible sieving performance. Accordingly, dextran gel should not be understood merely at the operational level of a “chromatographic packing material,” but should instead be considered systematically from the perspectives of its structural basis, specification differences, column-packing procedures, and application boundaries.

Keywords: dextran gel; gel filtration; crosslinked dextran; molecular sieving; desalting; buffer exchange; chromatographic packing material

1. Basic Concepts and Structural Basis of Dextran Gels

1.1 Material origin of dextran gels

(1) Dextran backbone

The fundamental material of dextran gel is dextran. Dextran is a hydrophilic polysaccharide composed of glucose residues and exhibits good aqueous compatibility and biocompatibility. Dextran itself is water-soluble, but after crosslinking it can form an insoluble three-dimensional network structure, thereby becoming a gel matrix suitable for chromatographic separation.

(2) Spatial network after crosslinking

After appropriate crosslinking, dextran no longer exists as a linear soluble polysaccharide, but forms a spatial network structure containing pores. This structure can both absorb water and swell, while still maintaining stable particle morphology, which is the direct structural basis for its use as a bioseparation medium. In other words, the separation performance of dextran gels does not arise solely from the material itself, but from the combined action of a hydrophilic backbone and a porous network.

1.2 Structural characteristics of dextran gels

(1) Hydrophilicity and low nonspecific adsorption

The dextran backbone is rich in hydroxyl groups and is therefore strongly hydrophilic overall. In conventional buffer systems, this property helps reduce nonspecific adsorption of biomacromolecules such as proteins, polysaccharides, and nucleic acids, so that the separation process more closely reflects size exclusion itself.

(2) Swellability

Dextran gels have a relatively small volume in the dry state. After absorbing water, the internal network gradually expands, forming a pore-channel system into which sample molecules can enter. Swelling is not merely simple water uptake, but the actual establishment of the working structure of the gel. Therefore, the pore structure of dextran gels is essentially further unfolded through hydration and swelling on the basis of crosslinking.

(3) Adjustable pore size

One of the most important structural features of dextran gels is tunable pore size. Different degrees of crosslinking correspond to different extents of network opening, thereby conferring different applicable separation ranges. When the degree of crosslinking is higher, the gel is more compact and the pore size is smaller; when the degree of crosslinking is lower, the gel exhibits greater swelling and larger pore size, making it more suitable for sieving larger molecules.

1.3 Separation principles of dextran gels

(1) Molecular-sieving effect

The basic separation principle of dextran gels is the molecular-sieving effect. Molecules with relatively larger molecular mass cannot enter, or can only partially enter, the gel pores, and therefore mainly move through the interparticle spaces and elute more rapidly. Molecules with relatively smaller molecular mass can enter more of the pore space, are retained longer, and therefore elute more slowly.

(2) Differences in effective separation volume

Dextran gels do not rely on strong adsorption or chemical binding to accomplish separation. Their essence lies in the difference in accessible internal volume available to different molecules within the stationary phase. Large molecules mainly utilize the void volume outside the gel particles, whereas small molecules utilize both the external void volume and the internal pore volume of the gel. It is precisely this difference in effective separation volume that forms the basis of gel-filtration separation.

Table 1. Major structural characteristics of dextran gels and their separation significance

Structural characteristic	Material behavior	Separation significance
Hydrophilic backbone	Polyhydroxyl polysaccharide network	Reduces nonspecific adsorption and is suitable for aqueous systems
Three-dimensional crosslinked structure	Forms stable particles and pores	Provides the structural basis for molecular sieving
Swellability	Pore channels expand after hydration	Establishes effective separation volume
Adjustable pore size	Different crosslinking degrees yield different pore sizes	Covers separation needs for different molecular sizes
Good chemical inertness	Relatively stable in conventional buffer systems	Suitable for handling proteins, polysaccharides, nucleic acids, and related samples

2. Classification of Dextran Gels and Interpretation of Specifications

2.1 Naming rules of the G series

(1) Meaning of the G value

Crosslinked dextran gels are usually designated in the form “G + number.” The letter G represents the crosslinked dextran gel series, and the following Arabic numeral is related to the water uptake value of the gel. It can usually be understood as ten times the grams of water absorbed per gram of dry gel. For example, G-25 indicates that each gram of dry gel absorbs about 2.5 g of water, whereas G-200 indicates about 20 g.

(2) Structural information reflected by the G value

The G value is not merely a model number, but rather a composite reflection of gel crosslinking degree, swelling degree, and internal pore openness. In general, gels with smaller G values have higher crosslinking degree and smaller pore size, whereas gels with larger G values have higher swelling degree and larger pore size. Therefore, the larger the G value, the more suitable the gel usually is for entry and fractionation of larger molecules.

2.2 G-series specifications and separation behavior

(1) Low-G-value gels

G-10, G-15, and G-25 are dextran gels with relatively small pore sizes and are more suitable for desalting, small-molecule separation, and buffer exchange. Such gels usually exert a strong exclusion effect on target biomacromolecules, allowing large molecules to elute rapidly while salts and small-molecule impurities elute later.

(2) Medium- and high-G-value gels

G-50, G-75, G-100, G-150, and G-200 have progressively larger pore sizes and are more suitable for fractionation of proteins, polysaccharides, and macromolecular complexes, as well as relative molecular-mass analysis. The application focus of these gels is no longer merely removal of small molecules, but size-based fractionation through differences in accessible pore volume.

Table 2. Comparison of G-series crosslinked dextran gels in terms of specifications and structural characteristics

Model	Water absorbed per gram of dry gel (g)	Structural characteristics	Separation characteristics	Typical uses
G-10	1.0	High crosslinking degree, very small pore size	Small molecules enter more fully, large molecules are rapidly excluded	Rapid desalting, small-molecule separation, buffer exchange
G-15	1.5	Relatively high crosslinking degree, small pore size	Suitable for separation of low-molecular-weight species from salts	Desalting, removal of free low-molecular-weight impurities
G-25	2.5	Small pore size, moderate swelling	Good desalting performance for biomacromolecules	Desalting and buffer exchange of proteins, polysaccharides, and nucleic-acid samples
G-50	5.0	Larger pore size	Suitable for fractionation of small and medium-sized proteins	Separation of small proteins, peptides, and some polysaccharides
G-75	7.5	Higher swelling degree, larger pores	Suitable for protein separation over a relatively broad range	Routine protein fractionation and purification
G-100	10.0	Further enlarged pore size	Suitable for separation of medium to relatively large proteins	Separation of protein mixtures and molecular-weight estimation
G-150	15.0	High swelling degree, large pore size	More suitable for fractionation of large-molecule samples	Separation of large proteins, glycoproteins, and complexes
G-200	20.0	Highest swelling degree, largest pore size	Suitable for entry and separation of very high-molecular-weight samples	Separation of large protein complexes, polysaccharides, and polymers

2.3 Relationship among G value, crosslinking degree, swelling degree, and separation range

(1) G value and crosslinking degree

A smaller G value usually indicates a higher degree of crosslinking, a denser network, and smaller internal pore size. A larger G value usually indicates stronger water uptake and swelling capacity, together with more open pores.

(2) G value and application range

In practical applications, G-25 and lower specifications are commonly used for desalting and buffer exchange, whereas G-50 and above are more often used for protein fractionation and molecular-weight estimation. Therefore, selection of the G value should always be based on the relative molecular-mass range of the target molecules, rather than simply on an empirically “common model.”

3. Preparation Basis of Dextran Gels

3.1 Principles of dextran gel preparation

(1) Formation of a spatial network through crosslinking

The core of dextran gel preparation lies in transforming soluble dextran into an insoluble three-dimensional network material through crosslinking. The degree of crosslinking determines the compactness of the gel skeleton and also determines the size and uniformity of the pore channels formed after hydration.

(2) Pore structure forms jointly through crosslinking and swelling

The pore channels of dextran gels are not formed by simple mechanical perforation, but are gradually unfolded through hydration and swelling after the crosslinked skeleton has been established. Therefore, the final sieving performance of the gel depends not only on the crosslinking conditions, but also closely on the swelling conditions before use.

3.2 Key control points during preparation

(1) Raw-material purity

The purity of the dextran raw material directly affects gel uniformity. If the raw material contains excessive low-molecular-weight sugars, salts, or other impurities, this may result in uneven crosslinking, unstable particle morphology, or elevated background during subsequent elution.

(2) Crosslinking conditions

The amount of crosslinking agent, reaction time, and reaction environment determine the degree of crosslinking. If crosslinking is insufficient, the gel becomes too soft, swells excessively, and lacks adequate mechanical stability. If crosslinking is too strong, the pore size becomes too small and the effective separation range shifts markedly. Therefore, control of crosslinking is essentially a matter of balancing pore openness against skeleton stability.

(3) Particle formation and particle-size uniformity

Particle size and uniformity directly affect column-packing quality and fluid distribution. If the particle-size distribution is too broad, the packed bed is more prone to local differences in compaction and uneven flow velocity, ultimately resulting in peak broadening and lower resolution.

3.3 The concept of “preparation” in the laboratory context

(1) Narrow sense of preparation

In the narrow sense, preparation of dextran gels refers to obtaining the chromatographic matrix from dextran raw materials through processes such as crosslinking, granulation, washing, and drying.

(2) Broad sense of preparation

In actual laboratory practice, however, the more common meaning of “preparation” refers to pretreatment of ready-made dextran gels before use, including:

① swelling;

② removal of fines;

③ degassing;

④ column packing;

⑤ equilibration.

Therefore, when discussing “preparation and use methods,” the focus should usually be placed on establishment of the working state of the gel.

4. Methods for Using Dextran Gels

4.1 Pretreatment before use

(1) Swelling

Dry dextran gels usually need to be fully swollen in water or the appropriate buffer before use. The purposes include:

① fully unfolding the internal pores of the gel;

② allowing the particles to reach a stable volume;

③ preventing continued expansion after column packing that would otherwise alter the bed.

Different gel specifications require different swelling times, and the gel should be confirmed to have reached a stable volume before use.

(2) Removal of fines

After swelling, fines and suspended particles often need to be removed by decantation, sieving, or repeated washing. If too many fines remain, the packed column may exhibit elevated back pressure, local blockage within the bed, and peak broadening.

(3) Degassing

The gel suspension should preferably be degassed before column packing. If bubbles are introduced into the packed bed, they create local voids, disrupt uniform mobile-phase distribution, and cause discontinuity in the bed, thereby markedly reducing column efficiency.

4.2 Column-packing methods

(1) Wet packing

Dextran gels are usually packed by the wet-packing method. That is, a uniformly suspended gel slurry is slowly added into the chromatographic column, allowing the particles to settle naturally and gradually form a uniform packed bed. During packing, continuous liquid flow should be maintained as much as possible, and severe fluctuations of the liquid surface should be avoided.

(2) Packed-bed stabilization

After packing is completed, the bed should continue to be washed slowly with equilibration solution so that the particles become further compacted and reach a stable state. If the bed height continues to decrease markedly, this indicates that the gel has not yet settled completely, and equilibration should continue until the bed height becomes essentially stable.

(3) Evaluation of packed-bed quality

An ideal packed bed usually exhibits the following features:

① a level surface;

② no obvious cracks;

③ no bubbles or voids;

④ no obvious stratification;

⑤ stable changes in flow rate.

4.3 Equilibration and sample application

(1) Column equilibration

Before formal separation, the bed should be thoroughly equilibrated with a buffer compatible with the sample. Equilibration is used not only to replace the medium inside the column, but more importantly to allow the gel to reach a stable state under the actual ionic conditions of operation.

(2) Sample pretreatment

Before loading, samples should generally be centrifuged or filtered to remove particulate impurities and prevent bed blockage. At the same time, sample volume and viscosity should be controlled as much as possible to avoid excessive band broadening during loading, which would reduce resolution.

(3) Principles of sample loading

For gel-filtration separation, samples should generally be loaded in relatively small volumes and at moderate concentrations. If the loading volume is too large, the initial distribution zone of different components inside the column becomes significantly broadened, ultimately resulting in peak broadening and overlap of components.

4.4 Elution and fraction collection

(1) Elution mode

Dextran gels are usually operated under isocratic elution, that is, the same buffer is used continuously to drive the sample through the bed. Because the separation basis is the size-exclusion effect, separation does not usually rely on salt gradients or pH gradients.

(2) Elution order

Components with relatively larger molecular mass elute first, whereas those with relatively smaller molecular mass elute later. When dextran gels are used for desalting, the target biomacromolecule usually appears in the early elution peak, whereas salts and small-molecule impurities elute later.

(3) Fraction collection and detection

The eluate should be collected in fractions by volume, and the location of the target component should be determined using UV absorbance, conductivity, or corresponding activity assays. Protein samples are commonly monitored at 280 nm, whereas desalting experiments are often accompanied by conductivity detection to evaluate salt removal.

4.5 Regeneration and storage

(1) Regeneration of the packed bed

After use, the packed bed may be regenerated with an appropriate buffer or mild cleaning system depending on sample properties, so as to remove residual adsorbed substances and contaminants. If residual sample remains for prolonged periods, column efficiency may decline and separation reproducibility may worsen.

(2) Storage conditions

Dextran gels should generally be stored in the wet state and in an appropriate preservative system in order to prevent microbial contamination and drying-induced cracking. If stored dry for long periods, they should be fully reswollen and re-equilibrated before reuse.

Table 3. Workflow for use of dextran gels and key control points

Stage of use	Main operations	Key control points
Pretreatment	Swelling, removal of fines, degassing	Establish a stable pore structure and reduce fines and bubbles
Column packing	Wet packing, bed compaction	Ensure a uniform packed bed without cracks or voids
Equilibration	Buffer equilibration	Establish a stable working ionic environment
Sample loading	Sample clarification, volume control	Prevent blockage and avoid excessively broad sample bands
Elution	Isocratic elution, fraction collection	Control flow rate and improve resolution
Regeneration and storage	Cleaning, preservation, wet storage	Maintain column efficiency and stability during repeated use

5. Major Applications of Dextran Gels

5.1 Desalting and buffer exchange

(1) Desalting of biomacromolecules

One of the most classical applications of dextran gels is rapid desalting of proteins, polysaccharides, nucleic acids, and enzyme preparations. The principle is that large target biomolecules are excluded from the gel pores and therefore elute first, whereas inorganic salts, low-molecular-weight reducing agents, and buffer components enter the gel interior and elute later.

(2) Buffer-system conversion of samples

In protein purification and enzymology experiments, samples often need to be transferred from a high-salt system to a low-salt system, or from an incompatible buffer to one required for subsequent experiments. Dextran gels can accomplish this under relatively mild conditions and are usually faster than dialysis.

5.2 Fractionation and purification of biomacromolecules

(1) Protein separation

When the target protein differs significantly in molecular size from contaminating proteins, dextran gels can be used for protein fractionation and purification. Their advantages include mild separation conditions, a clear separation principle, and relatively limited effects on native protein conformation and activity.

(2) Separation of polysaccharides and complex samples

Dextran gels are likewise suitable for preliminary size-based fractionation of polysaccharides, glycoproteins, or protein complexes. Particularly when crude extracts are complex and sample complexity must first be reduced according to size, dextran gels are often used as a front-end purification tool.

5.3 Molecular-weight estimation and homogeneity analysis

(1) Estimation of relative molecular mass

By establishing the relationship between elution volume and molecular size using known standards, it is possible to estimate the relative molecular mass of unknown samples. This application is highly useful in analysis of protein aggregation states, determination of molecular-weight ranges of polysaccharides, and studies of polymer distributions.

(2) Evaluation of sample aggregation and heterogeneity

Dextran gels can also be used to determine whether samples exhibit aggregation, degradation, or oligomer formation. If the elution peak shows marked forward shift, tailing, or multiple peaks, this often indicates size heterogeneity in the sample.

5.4 Pretreatment of biological samples and analytical support

(1) Removal of interfering small molecules

In many analytical experiments, free substrate, free dye, reducing agents, nucleotides, and other small molecules in the sample may interfere with downstream detection. Dextran gels can serve as a mild and efficient pretreatment method for removal of such low-molecular-weight background components.

(2) Intermediate conditioning step in multistep purification workflows

In practical processes, dextran gels often do not serve as the terminal high-purity separation step, but are more often used for intermediate conditioning: carrying out desalting, buffer exchange, crude fractionation, and removal of low-molecular-weight impurities, thereby creating more suitable sample conditions for subsequent ion exchange, affinity chromatography, or reversed-phase purification.

Table 4. Typical application scenarios of dextran gels

Application direction	Main objects	Core purpose
Desalting	Proteins, polysaccharides, nucleic acids	Remove inorganic salts and low-molecular-weight impurities
Buffer exchange	Biomacromolecular samples	Replace the system to meet downstream experimental requirements
Fractionation and purification	Proteins, polysaccharides, complex samples	Achieve preliminary size-based separation
Molecular-weight analysis	Standards and unknown samples	Estimate relative molecular mass and distribution
Pretreatment	Biological samples containing interfering small molecules	Reduce sample complexity and improve detection accuracy

6. Related Research Products

Table 5. Key CAS reagents used in dextran-gel-related research

Name	CAS No.	Experimental stage	Key use	Use notes
Dextran	9004-54-0	Matrix raw material/methodological research	Used as the basic polysaccharide backbone material of dextran gels for studies of gel structure, swelling behavior, and crosslinking precursors	More suitable for basic materials studies and method development
Blue dextran 2000	87915-38-6	Column-volume determination/exclusion-volume marker	Used to determine void volume of the packed bed and evaluate the external void volume and packing state of dextran-gel columns	Commonly used as a large-molecule exclusion marker
Sodium dihydrogen phosphate	7558-80-7	Buffer preparation	Used to construct the buffer environment required for gel filtration and equilibration	Suitable for preparation of neutral or weakly acidic buffer systems
Disodium hydrogen phosphate	7558-79-4	Buffer preparation	Used with sodium dihydrogen phosphate to establish phosphate buffer systems	Suitable for routine aqueous separation systems
HEPES	7365-45-9	Buffer preparation	Suitable for constructing neutral systems with relatively stable buffering capacity for protein-sample gel filtration	Commonly used in systems requiring high pH stability
MES	4432-31-9	Buffer preparation	Suitable for sample separation and equilibration under mildly acidic conditions	Suitable for certain protein or enzyme systems
MOPS	1132-61-2	Buffer preparation	Suitable for construction of buffering systems near neutrality and for design of mild separation conditions	Commonly used for processing proteins and nucleic acids
Sodium acetate	127-09-3	Buffer preparation	Used with acetic acid to prepare acetate buffer systems	Suitable for sample equilibration and elution under low-pH conditions
Sucrose	57-50-1	Small-molecule removal model/sample stabilization	Used to simulate retention behavior of soluble-sugar impurities or sample stabilizers in dextran gels	Suitable for validation in desalting and buffer-exchange experiments
Glucose	50-99-7	Small-molecule removal model	Used to evaluate the separation behavior of dextran gels toward monosaccharides	Suitable as a low-molecular-weight model compound entering pores
Ammonium sulfate	7783-20-2	Sample pretreatment/desalting validation	Commonly used for validating removal of high-salt background after protein precipitation	Suitable for use with protein-desalting experiments
Bovine serum albumin	9048-46-8	Column-efficiency validation/molecular-weight reference	Used as a model sample in protein separation and desalting experiments	Suitable as a medium-molecular-weight standard protein
Ovalbumin	9006-59-1	Molecular-weight reference	Used to establish an elution-behavior reference for proteins in the medium molecular-weight range	Suitable for combined use with other standard proteins to build calibration curves
Lysozyme	12650-88-3	Molecular-weight reference	Used for calibration of separation and elution behavior in the smaller protein range	Suitable for evaluating separation ability for small and medium-sized proteins
Cytochrome c	9007-43-6	Molecular-weight reference	Used to establish elution-behavior references for proteins in gel columns	Suitable for combined use with other standard proteins
Ribonuclease A	9001-99-4	Molecular-weight reference	Used for calibration of elution volume in the small-protein range	Suitable for establishing fractionation models
Catalase	9001-05-2	Large-protein reference	Used for evaluating separation behavior in the larger protein range	Suitable for combined range validation together with medium- and small-sized protein standards
Ferritin	9007-73-2	Large-molecule separation reference	Used for evaluation of elution behavior in the high-molecular-weight protein range	Suitable for validation of separation ranges of larger-pore dextran gels
Vitamin B12	68-19-9	Small-molecule marker	Used to validate complete entry behavior of small molecules in dextran gels	Commonly used in validation of desalting and separation boundaries

Table 6. Product table related to dextran gels

Catalog No.	Name	Grade and Purity	Type positioning	Research direction / intended use
S189680	Dextran Gel	40-120 μm, separation range <1500 (globulin)	Small-molecule separation-type dextran gel	Suitable for gel filtration, desalting, and removal of low-molecular-weight impurities in lower-molecular-weight sample ranges, and can also be used to establish models of sieving behavior for small-pore dextran gels
B300413	Dextran Gel	40-120 µm, ion-exchange capacity 2.0-2.6 mmol/g (dry gel)	Ion-exchange-type dextran gel	More suitable for inclusion in the context of functionalized dextran-matrix research, for comparison of size-exclusion and ion-exchange composite separation behavior, and should not be placed within the main line of simple gel filtration
S195743	Dextran Gel	40-120 μm, separation range <700 (globulin)	Very-small-pore separation-type dextran gel	Suitable for smaller-molecule separation, desalting, and buffer exchange in lower-molecular-weight ranges, and can also serve as a small-pore control material for comparison of exclusion behavior among gels
S304940	Dextran Gel	40-120 μm, separation range 3000-120000 (globulin)	Medium- to large-pore fractionation-type dextran gel	Suitable for gel-filtration fractionation of proteins, polysaccharides, and medium-molecular-weight samples, and can be used to illustrate the structural transition of dextran gels from desalting type to fractionation type
S489270	Sephadex G-50	Medium	G-50 medium-particle fractionation type	Suitable for routine fractionation and purification of small and medium-sized proteins, peptides, and some polysaccharides, and is a representative entry illustrating the correspondence between G-series structure and application
C1451462	Cross-linked dextran G 150	—	G-150 large-pore fractionation type	Suitable for separation of relatively large proteins, glycoproteins, and complex samples, and can be used to illustrate the high swelling degree and large-pore structural features of high-G-value gels
C1453456	Cross-linked dextran G 200	—	G-200 very-large-pore fractionation type	Suitable for separation of higher-molecular-weight samples, protein complexes, and polymer samples, and appropriate for exemplifying the application boundary of large-pore dextran gels
S665614	Sephadex® G-100	Medium	G-100 medium-particle fractionation type	Suitable for routine protein fractionation and relative molecular-weight estimation, and can serve as an intermediate specification between G-75 and G-150
S665608	Sephadex® G-100	BioReagent, DNA grade, molecular biology grade, medium	G-100 molecular-biology grade	Suitable for separation and desalting of nucleic-acid- and DNA-related samples and for molecular-biology pretreatment, illustrating the extended application of dextran gels in molecular-biology systems
S665441	Sephadex® G-100	Superfine	G-100 high-resolution type	Suitable for protein separation and analytical gel-filtration experiments requiring higher resolution, and can be used to illustrate the influence of particle grade on column efficiency
B301074	Diethylaminoethyl Sephadex A25	—	DEAE-functionalized dextran gel	More suitable for inclusion in the context of functionalized dextran derivatives, illustrating that dextran can serve not only as a sieving medium but also as an ion-exchange medium after derivatization
S311115	Sephadex G-25	BioReagent, coarse	G-25 coarse-particle desalting type	Suitable for rapid desalting and pretreatment of large-volume samples, with greater emphasis on throughput and operational convenience
S310922	Sephadex G-25	BioReagent, fine	G-25 fine-particle desalting type	Suitable for applications requiring desalting together with a certain level of resolution, and useful for comparing the effects of particle grade on column efficiency and flow rate
S293471	Sephadex G-25	BioReagent, medium particle	G-25 medium-particle desalting type	Suitable for routine desalting and buffer exchange of proteins, polysaccharides, and nucleic-acid samples, and one of the most typical dextran-gel entries for desalting applications
S303577	Sephadex G-75	Medium particle	G-75 medium-pore fractionation type	Suitable for routine fractionation and purification of proteins over a relatively broad range, and can serve as a representative model between G-50 and G-100
S489303	Sephadex® G-50	Superfine	G-50 high-resolution type	Suitable for higher-resolution fractionation of small and medium-sized proteins, and also useful for illustrating that finer particles usually improve column efficiency while increasing flow resistance
S489267	Sephadex G-50	BioReagent, DNA grade, molecular biology grade, medium	G-50 molecular-biology grade	Suitable for molecular-biology sample pretreatment, desalting of nucleic-acid-related samples, and separations in the small- to medium-molecular-weight range
S489265	Sephadex G-50	BioReagent, DNA grade, molecular biology grade, fine	G-50 fine-particle molecular-biology grade	Suitable for molecular-biology applications requiring both relatively high resolution and good sample compatibility
S420151	Sephadex G-50	Fine	G-50 fine-particle fractionation type	Suitable for refined fractionation of routine protein samples, and can be listed together with Medium and Superfine grades to illustrate the effect of particle grade on application scenarios

Overall, the application value of dextran gels does not lie merely in their ability to perform gel filtration, but in their integration of desalting, buffer exchange, fractionation and purification, and molecular-weight analysis within one stable hydrophilic porous material system. The key to understanding their use lies not in simply memorizing model numbers and operating steps, but in accurately grasping the correspondence among matrix structure, pore characteristics, separation principles, and operational control points.

For more related articles, please see below:

[1] Selection of Separation Media in Protein Purification: Principles and Applications of Chromatography Resins and Magnetic Beads