The conformation and structure of GAGs: recent progress and perspectives.

The glycosaminoglycan (GAG) family of linear sulphated polysaccharides are involved in most regulatory processes in the extracellular matrix of higher organisms. The relationship between GAG substitution pattern and activity, however, remains unclear and experimental evidence suggests that subtle conformational factors play an important role. The difficulty of modelling these complex charged molecules shifts the burden of investigation towards experimental techniques. Recent advances in complementary physical-chemical, particularly spectroscopy-based approaches are reviewed, together with methods for analysing the resulting complex data. The prospects for combining some of these approaches and fitting them into the wider context of interactions, are also discussed.

Site-specific interactions of copper(II) ions with heparin revealed with complementary (SRCD, NMR, FTIR and EPR) spectroscopic techniques.

The interactions between Cu(II) ions and heparin were investigated using several complementary spectroscopic techniques. NMR indicated an initial binding phase involving specific coordination to four points in the structure that recur in slightly different environments throughout the heparin chain; the carboxylic acid group and the ring oxygen of iduronate-2-O-sulfate, the glycosidic oxygen between this residue and the adjacent (towards the reducing end) glucosamine and the 6-O-sulfate group. In contrast, the later binding phase showed little structural specificity. One- and two-dimensional correlated FTIR revealed that complex out of phase (asynchronous) conformational changes also occurred during the titration of Cu(II) ions into heparin, involving the CO and N-H stretches. EPR demonstrated that the environments of the Cu(II) ions in the initial binding phase were tetragonal (with slightly varied geometry), while the later non-specific phases exhibited conventional coordination. Visible spectroscopy confirmed a shift of the absorbance maximum. Titration of Cu(II) ions into a solution of heparin indicated (both by analysis of FTIR and EPR spectra) that the initial binding phase was complete by 15-20 Cu(II) ions per chain; thereafter the ions bound in the non-specific mode. Hetero-correlation spectroscopy (FTIR-CD) improved resolution and assisted assignment of the broad CD features from the FTIR spectra and indicated both in-phase and more complex out of phase (synchronous and asynchronous, respectively) changes in interactions within the heparin molecule during the titration of Cu(II) ions.

High sensitivity separation and detection of heparan sulfate disaccharides.

Eight Delta-disaccharide standards from heparan sulfate/heparin were derivatized with the fluorophore 4,4-difluoro-5,7- dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid, hydrazide (BODIPY) via formation of a Schiff's base and separated using HPAEC on a Propac PA1 column with a linear salt gradient and isocratic 150 mM NaOH. Detection was with an in-line fluorescence detector. The standard deviation (sigma(n-1)) in retention times were 0.7-2% over nine runs. The limit of detection, was 100 fmol (100 x 10(-15)mol) of BODIPY labeled Delta-disaccharides, representing considerably improved detection compared to other fluorophore labeled derivatives and, unlike these, required no further purification steps. Separation and improved detection of BODIPY-Delta-disaccharide conjugates will assist the structural analysis of HS and the development of improved sequencing methodologies.

Protein-GAG interactions: new surface-based techniques, spectroscopies and nanotechnology probes.

New approaches, rooted in the physical sciences, have been developed to gain a more fundamental understanding of protein-GAG (glycosaminoglycan) interactions. DPI (dual polarization interferometry) is an optical technique, which measures real-time changes in the mass of molecules bound at a surface and the geometry of the bound molecules. QCM-D (quartz crystal microbalance-dissipation), an acoustic technique, measures the mass and the viscoelastic properties of adsorbates. The FTIR (Fourier-transform IR) amide bands I, II and III, resulting from the peptide bond, provide insight into protein secondary structure. Synchrotron radiation CD goes to much shorter wavelengths than laboratory CD, allowing access to chromophores that provide insights into the conformation of the GAG chain and of beta-strand structures of proteins. To tackle the diversity of GAG structure, we are developing noble metal nanoparticle probes, which can be detected at the level of single particles and so enable single molecule biochemistry and analytical chemistry. These new approaches are enabling new insights into structure-function relationships in GAGs and together they will resolve many of the outstanding problems in this field.

Home intravenous dobutamine therapy in patients awaiting heart transplantation.

Lack of donor availability has heightened our awareness of the need for suitable long-term management of heart failure in patients awaiting heart transplantation. Frequently patients become dependent on intravenous inotropic agents despite attempts to discontinue these agents. This can lead to prolonged hospitalizations, separation anxiety and depression in families, high hospitalization costs, and poor quality of life. Between June 1987 and April 1988 three patients awaiting heart transplantation at the University of Cincinnati Hospital were sent home while receiving constant intravenous infusion of dobutamine. All three patients had had prolonged hospitalizations and were unable to be weaned from dobutamine without clinical compromise. The patients were New York Heart Association functional class III to IV, had cardiac indices between 1.5 to 2.13 L/min/m2, cardiac output less than 4.0 L/min, pulmonary capillary wedge pressures 17 to 27 mm Hg, and left ventricular ejection fraction less than 20% in two of the patients (idiopathic cardiomyopathy), and 30% in the third patient who was awaiting retransplantation (refractory repeated acute rejections). Dobutamine was infused by means of a constant-rate portable cassette pump at 3.17 micrograms/kg/min in patient 1, 10 micrograms/kg/min in patient 2, and 5 micrograms/kg/min in patient 3. A critical care home health nursing agency was used for follow-up home care. All three patients had central lines placed before discharge from the hospital. Each patient was instructed in proper care of the central line and infusion pump and was able to demonstrate accurate technique before being discharged home. Complications were minimal and were related to central line placement. No patient required rehospitalization for complications. No wound infections were reported.(ABSTRACT TRUNCATED AT 250 WORDS)