Gel Permeation Chromatography

Impact of refractive index increment on the determination of molecular weight of hyaluronic acid by muti-angle laser light-scattering technique

Hyaluronic acid (HA) is applied in a number of medical applications and HA of different molecular weight (Mw) are used in different pharmaceutical preparations. In determination of Mw by muti-angle laser light-scattering (MALS), refractive index increment (dn/dc) is an important parameter for accuracy. Herein, the influence of dn/dc on the Mw of HA in stroke-physiological saline solution is investigated by MALS in this work. Additionally, the Mw variation of HA in the manufacturing process of preparations is measured. It is shown that each HA sample corresponds to a specific value of dn/dc, which is varied from 1.38 to 1.74 L/g with the Mw increasing from 13.5 to 2840 kDa in solution. It is indicated by the results from both MALS approach and viscometry that appropriate dn/dc should be selected for Mw determination. In steam sterilization process of preparations at 121 °C, the Mw and conformation of HA can be accurately and rapidly determined by MALS. This work provides a precise method to determine the Mw of HA in the medical applications and preparation industries.

Size-exclusion-chromatography separation of randomly branched polymers with tetrafunctional branch points and local dispersity

The SEC separation of a randomly branched polymer, in particular local dispersity due to branching, are theoretically examined. A model of the SEC separation of randomly branched polymer with tetrafunctional branch points enabling the estimation of local dispersity was developed. Measurable quantities (branching indices) were compared with real data. Local dispersity due to branching is demonstrated to depend on elution volume and degree of branching and in the area of the beginning of the elution curve it can reach non-negligible values.

Nanotechnology for the biologist

Nanotechnology refers to research and technology development at the atomic, molecular, and macromolecular scale, leading to the controlled manipulation and study of structures and devices with length scales in the 1- to 100-nanometers range. Objects at this scale, such as "nanoparticles," take on novel properties and functions that differ markedly from those seen in the bulk scale. The small size, surface tailorability, improved solubility, and multifunctionality of nanoparticles open many new research avenues for biologists. The novel properties of nanomaterials offer the ability to interact with complex biological functions in new ways-operating at the very scale of biomolecules. This rapidly growing field allows cross-disciplinary researchers the opportunity to design and develop multifunctional nanoparticles that can target, diagnose, and treat diseases such as cancer. This article presents an overview of nanotechnology for the biologist and discusses "nanotech" strategies and constructs that have already demonstrated in vitro and in vivo efficacy.

Problems connected with band-broadening in size-exclusion chromatography with dual detection

The sources of band-broadening (axial dispersion) in size-exclusion chromatography (SEC) of polymers and its influence on data obtained using dual detection of concentration and molecular weight are reviewed. Special attention is paid to the combination of a multiangle light-scattering photometer and a differential refractometer as detectors. The local polydispersity is discussed in the relation to the band-broadening as well as to heterogeneity of the polymer with respect to molecular weight and hydrodynamic volume.

Universal calibration of gel permeation chromatography and determination of molecular shape in solution

Gel permeation chromatography (GPC) has become a routine technique for both biology and polymer chemistry. By comparison our theoretical perception of the separation principle of GPC is still immature and conflicting and so is the assessment of the analytical informational content of this method. In order to discriminate between the various parameters that might influence GPC and thus to decide among the numerous propositions of calibration, several odd biopolymers (tropomyosin, spectrin, DNA, tobacco mosaic virus, alpha-actinin, ovomucoid) were selected. They were characterized by analytical ultracentrifugation as well as quasielastic light scattering, and they were compared to globular proteins including icosahedral viruses (tomato bushy stunt virus, turnip yellow mosaic virus, Q beta, MS2) on several different HPLC column matrices. The results demonstrate that the universal calibration principle of GPC is the viscosity radius, i.e., the molecular volume times a shape function which is defined by the intrinsic viscosity. Alternate propositions such as molecular weight, second virial coefficient, diffusion coefficient (Stokes radius), radius of gyration, mean linear projected length, contour length, and related measures seem to be excluded on the basis of the evidence presented. These results help to focus the physical picture which seems to govern GPC. Finally it is demonstrated that GPC is a versatile and unique tool with which to characterize molecular shape and dynamics in solution.

Liquid Chromatography in 1982

Classical liquid chromatography gave rise 15 years ago to new ideas about high-speed separations. Today, difficult separations can be made almost routinely by use of liquid chromatography instruments with automated controls and sensitive detectors. Sorptive effects are often best achieved with small, porous, "bonded phase" particles. The trend is to control the chemical selectivity by means of the liquid phase. These techniques are easily learned, and they have been widely accepted throughout chemistry and its allied disciplines. As a result, liquid chromatography has become the most rapidly expanding branch of the chemical instrumentation field.

Cascade chromatography and automated multidimensional fractionation

A general method of automated multidimensional fractionation has been developed. Its basic ingredients are: (a) cascade fractionation, i.e., the sequential fractionation of components obtained from each chromatographic dimension on the same or a different dimension, (b) on-line acquisition and processing of data at each stage in the fractionation procedure, (c) a method for determining the beginning and end of each peak during column elution, and (d) automatic linkage of the successive stages in a chemical fractionation scheme based on information obtained before or during each stage. Apparatus for automatic cascade chromatography and conditional fractionation is described. The method can be extended to provide completely automatic separation of pure components from complex mixtures.