RP-HPLC Reversed-Phase High-Performance Liquid Chromatography

Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC)

Reversed-phase high-performance liquid chromatography (RP-HPLC) involves the separation of molecules on the basis of hydrophobicity. The separation depends on the hydrophobic binding of the solute molecule from the mobile phase to the immobilized hydrophobic ligands attached to the stationary phase, i.e., the sorbent.

Separation of Molecules Using RP-HPLC

The solute mixture is initially applied to the sorbent in the presence of aqueous buffers, and the solutes are eluted by the addition of organic solvent to the mobile phase. Elution can proceed either by isocratic conditions where the concentration of organic solvent is constant, or by gradient elution whereby the amount of organic solvent is increased over a period of time. The solutes are, therefore, eluted in order of increasing molecular hydrophobicity. RP-HPLC is a very powerful technique for the analysis of peptides and proteins because of a number of factors that include: (1) the excellent resolution that can be achieved under a wide range of chromatographic conditions for very closely related molecules as well as structurally quite distinct molecules; (2) the experimental ease with which chromatographic selectivity can be manipulated through changes in mobile phase characteristics; (3) the generally high recoveries and, hence, high productivity; and (4) the excellent reproducibility of repetitive separations carried out over a long period of time, which is caused partly by the stability of the sorbent materials under a wide range of mobile phase conditions. However, RP-HPLC can cause the irreversible denaturation of protein samples thereby reducing the potential recovery of material in a biologically active form. The RP-HPLC experimental system for the analysis of peptides and proteins usually consists of an n-alkylsilica-based sorbent from which the solutes are eluted with gradients of increasing concentrations of organic solvent such as acetonitrile containing an ionic modifier such as trifluoroacetic acid (TFA). Complex mixtures of peptides and proteins can be routinely separated and low picomolar—femtomolar amounts of material can be collected for further characterization. Separations can be easily manipulated by changing the gradient slope, the operating temperature, the ionic modifier, or the organic solvent composition.

What can RP-HPLC Separate?

The extensive use of RP-HPLC for the purification of peptides, small polypeptides with molecular weights up to 10,000, and related compounds of pharmaceutical interest has not been replicated to the same extent for larger polypeptides (molecular mass > 10 KDa) and globular proteins. The combination of the traditionally used acidic buffering systems and the hydrophobicity of the n-alkylsilica supports which can result in low mass yields or the loss of biological activity of larger polypeptides and proteins have often discouraged practitioners from using RP-HPLC methods for large-scale protein separations. The loss of enzymatic activity, the formation of multiple peaks for compositionally pure samples, and poor yields of protein can all be attributed to the denaturation of protein solutes during the separation process using RP-HPLC. RP-HPLC is extremely versatile for the isolation of peptides and proteins from a wide variety of synthetic or biological sources and is used for both analytical and preparative applications. Analytical applications range from the assessment of purity of peptides following solidphase peptide synthesis, to the analysis of tryptic maps of proteins.

Preparative RP-HPLC

Preparative RP-HPLC is also used for the micropurification of protein fragments for sequencing to large-scale purification of synthetic peptides and recombinant proteins. The complexity of the mixture to be chromatographed will depend on the nature of the source and the degree of preliminary clean-up that can be performed. In the case of synthetic peptides, RP-HPLC is generally employed both for the initial analysis and the final large-scale purification. The purification of synthetic peptides usually involves an initial separation on an analytical scale to assess the complexity of the mixture followed by large-scale purification and collection of the target product. A sample of the purified material can then be subjected to RP-HPLC analysis under the same or different elution conditions to check for purity. The isolation of proteins from a biological cocktail derived from a tissue extract or biological fluid for example, often requires a combination of techniques to produce a homogenous sample. HPLC techniques are then introduced at the later stages following initial precipitation, clarification, and preliminary separations using soft gels. The challenge facing the scientist who wishes to analyze and/or purify their peptide or protein sample by RP-HPLC is the selection of the initial separation conditions and subsequent optimization of the appropriate experimental parameters.

Gel Filtration Chromatography

Proteins that differ in mass can be separated by Gel Filtration Chromatography.

Gel Filtration Chromatography Background Information

Proteins that differ in mass can be separated by gel filtration chromatography.<span>  In this technique, the column is composed of porous beads made from polyacrylamide, dextran (a bacterial polysaccharide), or agarose (a seaweed derivative). Proteins flow around the spherical beads in gel filtration chromatography.However the surface if the beads is punctured by large holes, and proteins will spend some time withing these holes. Because smaller proteins can penetrate into the beads more easily than larger proteins, they travel through a gel filtration column more slowly than larger proteins. (In contrast, proteins migrate through the pores in a electrophoretic gel; thus smaller proteins move faster than larger ones.) The total volume of liquid required to elute a protein from the column depends on its mass; the smaller the mass, the greater the elution volume. By use of proteins of known mass, the elution volume can be used to estimate the mass of a protein in a mixture.

HPLC of Peptides and Proteins: Basic Theory and Methodology

HPLC of Peptides and Proteins

High-performance liquid chromatography (HPLC) is the premier technique for the analysis and purification of a wide range of molecules. In particular, HPLC in its various modes has become the central technique in the characterization of peptides and proteins and has, therefore, played a critical role in the rapid advances in the biological and biomedical sciences over the last 10 years. The enormous success of HPLC can be attributed to a number of important features associated with reproducibility, ease of selectivity manipulation, and generally high recoveries. The most significant feature is the excellent resolution that can be achieved under a wide range of conditions for very closely related molecules, as well as structurally quite distinct molecules. This arises from the fact that all interactive modes of chromatography are based on recognition forces that can be subtly manipulated through changes in the elution conditions that are specific for the particular mode of chromatography. Peptides and proteins interact with the chromatographic surface in an orientation specific manner, in which their retention time is determined by the molecular composition of specific contact regions. For larger polypeptides and proteins that adopt a significant degree of secondary and tertiary structure, the chromatographic contact region comprises a small proportion of the total molecular surface. Hence, the unique orientation of a peptide or protein at a particular stationary phase surface forms the basis of the exquisite selectivity that can be achieved with HPLC techniques. All biological processes depend on specific interactions between molecules and affinity chromatography exploits these specific interactions to allow the purification of a biomolecule on the basis of its biological function or individual chemical structure. In contrast reversed phase HPLC, ion-exchange and hydrophobic interaction chromatography separate peptides and proteins on the basis of differences in surface hydrophobicity or surface charge. These techniques therefore allow the separation of complex mixtures whereas affinity chromatography normally results in the purification of one or a small number of closely related components of a mixture. Reversed-phase chromatography (RPC) is arguably the most commonly used mode of separation for peptides, although ion-exchange (IEC) and size exclusion (SEC) chromatography also find application. The three-dimensional structure of proteins can be sensitive to the often harsh conditions employed in RPC, and as a consequence, RPC is employed less for the isolation of proteins where it is important to recover the protein in a biologically active form. IEC, SEC, and affinity chromatography are therefore the most commonly used modes for proteins, but RPC and hydrophobic interaction (HIC) chromatography are also employed. HPLC is extremely versatile for the isolation of peptides and proteins from a wide variety of synthetic or biological sources. The number of applications of HPLC in peptide and protein purification continue to expand at an extremely rapid rate. Solid-phase peptide synthesis and recombinant DNA techniques have allowed the production of large quantities of peptides and proteins which need to be highly purified. The design of multidimensional purification schemes to achieve high levels of product purity further highlight the power of HPLC techniques in the analysis and isolation of peptide and proteins samples. The complexity of the mixture to be chromatographed depends on the nature of the source and the degree of preliminary clean-up that can be performed. In the case of synthetic peptides, RPC is generally employed both for the initial analysis and the final large scale purification. The isolation of proteins from a biological cocktail however, often requires a combination of techniques to produce a homogenous sample. HPLC techniques are then introduced at the later stages following initial precipitation, clarification and preliminary separations using soft gel. Purification protocols therefore need to be tailored to the specific target molecule. The key factor that underpins the development of a successful separation protocol is the ability to manipulate the retention of the target molecule so that it can be resolved from other contaminating components. An outline of the general theory of chromatography and the factors that control both the retention time and peakwidth of solutes undergoing separation in terms of the parameters that control resolution. This information can then be used to understand the approaches used to perform separations with specific modes of chromatography.

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High performance liquid chromatography HPLC

High-performance liquid chromatography (HPLC) analysis of peptides and proteins has revolutionized science for 25 years by enabling the biological sciences the rapid and sensitive analysis of peptide and protein structure through the exquisite speed, sensitivity, and resolution that can be easily obtained. Today, HPLC in its various modes has become the pivotal technique in the characterization of peptides and proteins and currently plays a critical role in both our understanding of biological processes and in the development of peptide- and protein-based pharmaceuticals.

The number of applications of HPLC in peptide and protein purification continues to expand at an extremely rapid rate. Solid-phase peptide synthesis and recombinant DNA techniques have allowed the production of large quantities of peptides and proteins that need to be highly purified. HPLC techniques are also used extensively in the isolation and characterization of novel proteins that will become increasingly important in the post-genomic age. The design of multidimensional purification schemes to achieve high levels of product purity further demonstrates the power of HPLC techniques not only in the characterization of cellular events, but also in the production of peptide and protein-based therapeutics. HPLC continues to be at the heart of the analytical techniques with which scientists in both academia and in industry must arm themselves to be able to fully characterize the identity, purity, and potency of peptides and proteins.

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Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) information on the method.

Proteins that differ in mass can be separated by Gel Filtration Chromatography.

HPLC of Peptides and Proteins: Basic Theory and Methodology HPLC of Peptides and Proteins High-performance liquid chromatography (HPLC) is the premier technique for the analysis and purification of a wide range of molecules. In particular, HPLC in its various modes has become the central technique in the characterization of peptides and proteins and has, therefore, [...]

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Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC)