Small angle neutron scattering study of lysozyme-sodium dodecyl sulfate aggregates

The lysozyme-sodium dodecyl sulfate-water system features several interesting aggregation phenomena and is also of interest as it constitutes a model system for mixtures of a charged colloid with an oppositely charged surfactant, as both colloid and surfactant are pure and monodisperse compounds. The structure of such mixed protein - surfactant systems has been investigated by means of SANS contrast variation experiments. Two interesting issues of protein-surfactant aggregation are discussed. First, a new set of data on the structure of the protein-surfactant complex in solution is added to the discussion of whether the model of "beads on a necklace", "protein decorated micelles", or "flexible helix" is most appropriate. It is our conclusion that the compact globule of ysozyme does not fit well into any of the mentioned models. Instead, transient clusters of lysozyme-SDS aggregates are proposed for the L-1 phase and more strongly bound locally linear clusters for the gel phase. Second, the structure and formation of a homogeneous, transparent gel at room temperature is analyzed and compared to the well-studied heat-set globular gels. The gel structure in different ionic strengths, lower than the one caused by naturally occurring buffer salts has also been analyzed and it seems that small amounts of salt render the system a more repulsive character than salt-free conditions. In addition to the equilibrated samples studied with the contrast variation technique, the complexation has been studied over time

Morphology and molecular conformation in thin films of poly-gamma-methyl-L-glutamate at the air-water interface

The behavior of poly-gamma-methyl-L-glutamate (pMeE) at the air-water interface has been studied with the surface film balance technique. In addition, Langmuir-Blodgett (LB) films of pMeE deposited on mica and quartz have been studied by atomic force microscopy (AFM) and circular and linear dichroism (CD and LD) spectroscopy. Depending on the spreading solvent, pMeE displays strikingly different compression isotherms. When spread from chloroform or trifluoroacetic acid (TFA) the surface pressure isotherms are consistent with that of a peptide in a-helix conformation. However, the latter solvent gives rise to isotherms with a considerably smaller apparent mean molecular area, A(0). When spread from pyridine, on the other hand, pMeE yields an isotherm that is expanded and inconsistent with the presence of a monolayer consisting entirely of a-helical peptides. Isotherms and AFM images strongly suggest that peptide aggregation and solvent retention are the main factors behind the isotherm differences. When the water-soluble spreading solvent TFA is used, pMeE forms discrete wormlike aggregates embedded in a monolayer matrix. In the pyridine case, aggregation in the spreading solvent and retention of pyridine in the film result in a rough aggregate network coexisting with discrete aggregates. No aggregation takes place when chloroform is used as spreading solvent. CD and LD spectra of the LB films reveal a pronounced lateral orientation of the alpha-helices in films spread from chloroform and TFA, while spectra of films spread from pyridine are consistent with unordered peptide strands in beta-sheet conformation. In conclusion, the results show that if water-soluble and/or low-volatile solvents are used as spreading media, hydrophobic peptides cannot, a priori, be assumed to form proper monolayers

ONCOPOOL – a European database for 16,944 cases of breast cancer

ONCOPOOL is a retrospectively compiled database of primary operable invasive breast cancers treated in the 1990s in 10 European breast cancer Units. Sixteen thousand and nine hundred and forty four cases were entered, with tumours less than 5 cm diameter in women aged 70 or less (mean age 55). Data Data were date of birth, mode of diagnosis, pathology (size, lymph node status, grade, type, lympho-vascular invasion and hormone receptor) and therapies and outcome measures: first local, regional or distant recurrences, contralateral primary, date and cause of death. Tumour characteristics Mean diameter 1.8 cm, 66% lymph node negative, 24% 1–3 lymph nodes involved and 10% had 4 or more involved. Grade 1, 29%; Grade 2, 41%; and Grade 3, 30%. Polynomial relationships were established between grade, stage and size. Seventy-five percent were oestrogen receptor (ER) positive. ER closely related to grade. Outcomes Overall Survival was 89% at 5 years from diagnosis, 80% 10 years and 73% 15 years; Breast Cancer-Specific survivals were 91%, 84% and 79%. Survival strongly related to the Nottingham Prognostic Index (NPI).Cases detected at screening had 84% 10-year survival, those presenting symptomatically 76%. ER positive cases treated with adjuvant hormone therapy had a reduction in risk of death of 13% over those not receiving adjuvant therapy (p = 0.000). ER negative cases treated with chemotherapy showed a risk reduction of 23% over those not receiving chemotherapy (p = 0.000)