[Biological monitoring in the molding of plastics and rubbers]. / Monitoraggio biologico nello stampaggio di plastiche e gomme.

This survey was carried out in the molding of plastics and rubbers, in the "Professional Cancer Prevention Project" sponsored by the Lombardy region with the objective of developing and implementing protocols for evaluating exposure to carcinogens through the biological monitoring. The realities of molding the thermoplastic polymer ABS, rubber, and thermosetting plastics containing formaldehyde were examined. The carcinogenic substances identified in these processes were: 1,3-butadiene, acrylonitrile and styrene in molding ABS, polycyclic aromatic hydrocarbons (PAH) in molding rubber, and formaldehyde in molding the thermosetting plastics. Only for some of these substances biological indicators are available. The limited exposure to airborne chemicals in molding ABS and the intrinsic characteristics of biological indicators available for 1-3 butadiene have determined the non applicability of biological monitoring to this situation. The absence of a biological indicator of exposure to formaldehyde has made this situation not investigable. Exposure in the rubber molding was studied in 19 subjects applying the determination not metabolized PAH in urine. The levels of these indicators were similar to those measured in other groups of subjects without occupational exposure to PAH, confirming a low airborne contamination in this workplace.

Histamine and histidine determination in tuna fish samples using high-performance liquid chromatography. Derivatization with omicron-phthalaldehyde and fluorescence detection or UV detection of "free" species.

A rapid and simple HPLC procedure for the simultaneous determination of histamine and histidine is presented. Sample extraction, extract purification, derivatization and reversed-phase chromatographic determination are described. Also the analysis of "free" (i.e. not derivatized) species with UV detection is discussed, and the two procedures are compared. A derivatization step involves more difficulties in terms of linearity and reproducibility because of the great unstability of omicron-phthalaldehyde derivatives but presents many advantages due to the good separation between histamine and histidine as far as the increased sensitivity is concerned. The first results of canned tuna samples analysis are presented and discussed.

X-ray crystal structure of ferric Aplysia limacina myoglobin in different liganded states.

The X-ray crystal structure of the ligand-free ferric form of Aplysia limacina myoglobin (pH 6.0) has been refined at 1.7 A resolution (R = 15.1%), and its cyanide, thiocyanate and imidazole derivatives studied by difference Fourier techniques at atomic resolution. The crystallographic R-factors of the three different derivatives reported are 16.1%, 16.1% and 15.6% at 1.8 A, 2.0 A and 2.0 A resolution, respectively. The present results have been analyzed in parallel with previous crystallographic studies on the molecular structures of the fluoride and azide derivatives of ferric Aplysia limacina myoglobin. Ligand binding to the distal site of the heme pocket results in different networks of hydrogen bonds involving to various degrees the bound ligand, residue Arg(66)E10, the heme propionate III, ordered water molecules and/or protein backbone atoms from the CD region. In particular, Arg(66)E10 stabilizes the bound ligand and compensates for the absence of the hydrogen bond donor residue HisE7, commonly present in oxygen-carrying globins.

Crystal and molecular structure of the bovine alpha-chymotrypsin-eglin c complex at 2.0 A resolution.

The crystal structure of the complex between bovine alpha-chymotrypsin and the leech (Hirudo medicinalis) protein proteinase inhibitor eglin c has been refined at 2.0 A resolution to a crystallographic R-factor of 0.167. The structure of the complex includes 2290 protein and 143 solvent atoms. Eglin c is bound to the cognate enzyme through interactions involving 11 residues of the inhibitor (sites P5-P4' in the reactive site loop, P10' and P23') and 17 residues from chymotrypsin. Binding of eglin c to the enzyme causes a contained hinge-bending movement around residues P4 and P4' of the inhibitor. The tertiary structure of chymotrypsin is little affected, with the exception of the 10-13 region, where an ordered structure for the polypeptide chain is observed. The overall binding mode is consistent with those found in other serine proteinase-protein-inhibitor complexes, including those from different inhibition families. Contained, but significant differences are observed in the establishment of intramolecular hydrogen bonds and polar interactions stabilizing the structure of the intact inhibitor, if the structure of eglin c in its complex with chymotrypsin is compared with that of other eglin c-serine proteinase complexes.

Crystallization and preliminary data for the ferric form of Lucina pectinata hemoglobin I.

Cytoplasmic monomeric hemoglobin I from the bacteria-harboring gill of the bivalve mollusc Lucina pectinata has been crystallized in a form suitable for atomic resolution X-ray structural investigations. The crystals have been grown at pH 4.8, in 0.05 M-acetate buffer, using 2.6 M-ammonium sulfate as precipitating agent. The crystals belong to the monoclinic space group P2(1), with unit cell constants a = 50.0 A, b = 38.6 A, c = 42.1 A, beta = 107.1 degrees, and contain one molecule (14,000 Mr) in the asymmetric unit. By means of single crystal microspectrophotometry it has been shown that the crystals contain the ferric form of L. pectinata "sulfide reactive" hemoglobin I. On the other hand, by careful control of the buffering medium composition, it has been possible to obtain stable crystals of the deoxy, oxy and sulfide forms of the protein.

Crystallization of and preliminary X-ray data for the mouse major urinary protein and rat alpha-2u globulin.

Crystals of the mouse major urinary protein (MUP) and rat alpha-2u globulin (AMG) have been grown from solutions of polyethylene glycol 3350 and CdCl2, respectively. The crystals differ both in their morphologies and space groups but have very similar unit cell sizes. AMG crystallized in P2(1) (a = 56.6 A, b = 103.8 A, c = 62.7 A, beta = 95.1 degrees) with four subunits/asymmetric unit, while MUP gave crystals in P4(1)2(1)2 or P4(3)2(1)2 (a = 57.3 A, c = 109.9 A) with one subunit/asymmetric unit. Both crystal forms diffract beyond 2.8 A resolution.

X-ray crystal structure of the ferric sperm whale myoglobin: imidazole complex at 2.0 A resolution.

The X-ray crystal structure of the ferric sperm whale (Physeter catodon) myoglobin:imidazole complex has been refined at 2.0 A resolution, to a final R-factor of 14.8%. The overall conformation of the protein is little affected by binding of the ligand. Imidazole is co-ordinated to the heme iron at the distal site, and forces distinguishable local changes in the surrounding protein residues. His64(E7) swings out of the distal pocket and becomes substantially exposed to the solvent: nevertheless, it stabilizes the exogenous ligand by hydrogen bonding. The side-chains of residues Arg45(CD3) and Asp60(E3) are also affected by imidazole association.