Model for DNA Interactions with Proteins and Other Large Ligands: Extracting Physical Chemistry from Pure Mechanical Measurements.

We present a new model to describe DNA interactions with large ligands such as proteins, based on a quenched-disorder equation for ligand binding along the double helix and on Manning's description for the local changes of the persistence length at the binding sites. Such a model allows one to extract the physical chemistry of the interactions from pure mechanical measurements, such as those typically performed with DNA-protein complexes in force spectroscopy assays. We have tested the proposed methodology here to investigate the DNA interaction with the protein lysozyme, determining binding parameters such as the equilibrium association constant, the cooperativity degree of the binding reaction, and the fraction of neutralized charges on the phosphate backbone. The model also allows one to get information on the size and positional conformation of the bound proteins.

Controlling Cooperativity in ß-Cyclodextrin-DNA Binding Reactions.

We have investigated the interaction between the native neutral ß-cyclodextrin (CD) and the DNA molecule by performing single-molecule stretching experiments with optical tweezers. In particular, we have monitored the changes of the mechanical properties of the CD-DNA complexes as a function of the CD concentration in the sample. By using a quenched disorder statistical model, we were also capable to extract important physicochemical information (equilibrium binding constants, cooperativity degree) of such interaction from the mechanical data. In addition, we have found that the interaction occurs by two different mechanisms, first with the formation of relatively large CD clusters along the double helix, which thereafter can locally denature the DNA molecule by forming hydrogen bonds with the base pairs that eventually flip out. A prediction of our quenched disorder model was that cooperativity could be controlled by adjusting the surface charge of ß-CD molecules. This prediction is confirmed in the present work.

Alcoholic liver diseases in Portugal. Clinical and laboratory picture, mortality, and survival.

Six main types of histopathological changes were found in 463 patients with chronic alcoholism admitted during the 10-year period from 1966 to 1975: group I, normal liver in 2.6%; group II, fatty liver in 8.4%; group III, acute alcoholic hepatitis (AAH) in 7.6%; group IV, cirrhosis with or without steatosis in 68.7%; group V, cirrhosis with AAH in 12.8%; group VI, liver cell carcinoma (LCC) in 1.9% (all of the latter patients were also included in group IV). Seventy-three % were males and 27% were females. Females tended to be older than males. Cirrhosis was found in 68% of the group between 21 and 30 yr and in 85% between 51 and 60 yr. Normal histology or steatosis was less frequent after the age of 50 yr. Ascites and jaundice were more frequent in patients with AAH than in patients with steatosis. The majority of patients had SGOT under 100 karmen units/ml; SGPT was normal in 80% of patients with cirrhosis and higher than 100 karmen units/ml in 10%. SGPT was higher than SGOT in only 11.9% of the patients. Mortality was 46.7% according to the followup until 1978. Survival was 38.4% at the end of the first year and decreased very slowly afterwards to 32.8% in males and 11.5% in females after a 5-yr period.

[Isolated malignant lymphoma of the rectum(author's transl)]. / Isoliertes malignes Rektumlymphom

A case of primary and isolated, diffuse reticulosarcoma of the rectum is reported. There has been a history of blood diarrhea for 12 years in a 60 years old man, with no change in his general condition. Treatment with cyclophosphamide was started and maintained for two and a half years with complete local regression, and very good clinical results.