A Transparent, Interactive Software Environment for Communicating Life-Cycle Assessment Results: An Application to Residential Windows

Life-cycle assessments (LCAs) can be used to support the selection of environmentally preferable building materials. But the dominance of the usage phase in the life cycle of building materials represents a special challenge for two reasons. First, many aspects of a building material's usage phase can be context specific. Second, the LCA outcome may rest on a building material's service life, a parameter for which there is typically insufficient information for proper determination. For example, in the selection of a window, important usagephase, context-specific factors that could be determinant include lo-cation/climate, heating-system characteristics (efficiency and fuel), and product durability. A prototype software tool, the Life Cycle Explorer, has been developed that enables decision makers to assess the relative importance of literally dozens of such influential parameters in determining the outcomes of LCA evaluations for building components. The software employed by the Life Cycle Explorer permits extensive layering while maintaining ease of browsing, with the intent of accessibility to both the layperson and the expert. An initial application of the tool addressed residential window selection; the design principles of the software are relevant to the communication phase of a wide variety of LCA and industrial-ecologyrelated modeling projects.     

Amino acid-specific ADP-ribosylation. Sensitivity to hydroxylamine of [cysteine(ADP-ribose)]protein and [arginine(ADP-ribose)]protein linkages

Hydroxylamine stability has been used to classify (ADP-ribose)protein bonds into sensitive and resistant linkages, with the former representing (ADP-ribose)glutamate, and the latter, (ADP-ribose)arginine. Recently, it was shown that cysteine also serves as an ADP-ribose acceptor. The hydroxylamine stability of [cysteine([32P]ADP-ribose)]protein and [arginine([32P] ADP-ribose)]protein bonds was compared. In transducin, pertussis toxin catalyzes the ADP-ribosylation of a cysteine residue, whereas choleragen (cholera toxin) modifies an arginine moiety. The (ADP-ribose)cysteine bond formed by pertussis toxin was more stable to hydroxylamine than was the (ADP-ribose)arginine bond formed by choleragen. The (ADP-ribose)cysteine bond apparently represents a third class of ADP-ribose bonds. Pertussis toxin ADP-ribosylates the inhibitory guanyl nucleotide-binding regulatory protein (Gi) of adenylate cyclase, whereas choleragen modifies the stimulatory guanyl nucleotide-binding regulatory protein (Gs). These (ADP-ribose)protein linkages are identical in stability to those formed in transducin by the two toxins, consistent with the probability that cysteine and arginine are modified in Gi and Gs, respectively. Bonds exhibiting differences in hydroxylamine-stability were found in membranes from various non-intoxicated mammalian cells following incubation with [32P]NAD, which may reflect the presence of endogenous NAD:protein-ADP-ribosyl-transferases.     

Calmodulin-binding proteins: Visualization by I-calmodulin overlay on blots quenched with tween 20 or bovine serum albumin and poly(ethylene oxide)

To streamline detection of calmodulin-binding proteins, blotting techniques for the electrophoretic transfer of proteins onto nitrocellulose filters, followed by overlay with ¹²⁵I-calmodulin, have been adapted. Autoradiography of the ¹²⁵I-calmodulin-labeled blots allows the identification and quantitation of proteins that possess affinity for calmodulin. Five protocols for suppressing nonspecific binding and for enhancing specific interactions of ¹²⁵I-calmodulin with electrophoretically separated proteins were investigated. Tween 20 and bovine serum albumin alone, as well as combinations of bovine serum albumin and poly(ethylene oxide) or hemoglobin and gelatin, were evaluated as quenching and enhancing agents. Tween 20 proved highly effective for quenching nonspecific binding and for enhancing specific ¹²⁵I-calmodulin binding of a 61,000-M_r rat brain protein, which was only faintly observed on blots quenched with proteins alone. However, Tween 20 dissociated 50% of 68,000-M_r proteins and 80% of 21,000-M_r ¹²⁵I-labeled protein standards from the nitrocellulose filter. An alternative, the combination of bovine serum albumin followed by incubation with 15,000- to 20,000-M_r poly(ethylene oxide), proved satisfactory for the recovery of 61,000-M_r calmodulin-binding activity and for the detection of calmodulin-binding peptides (50,000 to 14,000 M_r) produced by limited proteolysis of rat brain 51,000-M_r calmodulin-binding protein. These blotting procedures for detection of calmodulin-binding proteins are compatible with a variety of one-dimensional and two-dimensional electrophoresis systems, including a two-dimensional electrophoresis system utilizing urea and sodium dodecyl sulfate in the first dimension and nonurea sodium dodecyl sulfate electrophoresis in the second, a system which proved useful for resolving calmodulin-binding proteins displaying anomalous electrophoretic migration in the presence of urea.     

Adenosine diphosphoribose transfer reactions catalyzed by Bungarus fasciatus venom NAD glycohydrolase

Reactions catalyzed by purified Bungarus fasciatus venom NAD glycohydrolase were demonstrated to include ADP-ribose transfer from NAD to alcohols and to imidazole derivatives to produce a variety of ADP-ribosides. The formation of products was monitored by high performance liquid chromatography. In the enzyme-catalyzed alcoholysis of NAD, the ratio of n-alkyl-ADP-riboside formed to the hydrolytic product, ADP-ribose, increased linearly with alcohol concentration. The effectiveness of alcohols as acceptors of the ADP-ribose moiety in these reactions increased with increasing chainlength of the alcohol used. Linear positive chainlength effects extended from methanol to pentanol suggesting facilitation of these reactions by nonpolar interactions. In the methanolysis reaction, NADP, thionicotinamide adenine dinucleotide, nicotinamide-1, N6-ethenoadenine dinucleotide, and 3-acetylpyridine adenine dinucleotide were shown to be as effective as NAD as donor substrates. The NAD glycohydrolase-catalyzed ADP-ribose transfer to pyridine bases to form NAD analogs was studied at pyridine base concentrations above those determined to be saturating for the base exchange reaction. Under these conditions, the ratio of base exchange to hydrolysis of NAD was directly related to the pKa of the ring nitrogen of the pyridine base employed. In addition to alcoholysis and pyridine-base exchange reactions, the snake venom enzyme was demonstrated to catalyze an ADP-ribose transfer reaction to imidazole derivatives. Arginine methyl ester was ineffective as an ADP-ribose acceptor molecule in these reactions.     

Oxygen fixation into hydroxyproline in etiolated maize seedlings : verification by tandem mass spectrometry

Etiolated maize (Zea mays L.) seedlings were grown in the dark for 5 days in an atmosphere enriched with 10.0 atom% ¹⁸O₂. Hydroxyproline was isolated from root and shoot tissues, purified, and methylated. It was not possible to determine ¹⁸O incorporation into hydroxyproline by conventional mass spectrometry because the final product was not sufficiently pure. The final product was analyzed successfully by tandem mass spectrometry. The ¹⁸O content of the hydroxyl oxygen atom was 10 ± 0.7 atom%. This result demonstrates that the hydroxyl oxygen atom in hydroxyproline was derived exclusively from molecular oxygen.     

Metabolic activation of the pneumotoxin, 3-methylindole, by vaccinia-expressed cytochrome P450s

Twelve human cytochrome P450s and one mouse P450 were produced in HepG2 cells using vaccinia virus cDNA expression and analyzed for their ability to bioactivate the pneumotoxin, 3-methylindole (3MI), to an electrophilic metabolite(s) which alkylated cellular macromolecules. Cell lysates containing CYP2C8, CYP3A4, CYP2A6 and CYP2F1 metabolized 3MI to an intermediate(s) that became covalently bound to lysate material. A control lysate produced from cells which had been infected with a wild-type vaccinia virus was not able to bioactivate 3MI. The mouse 1A2 enzyme metabolized 3MI at a rate of 75.4 pmol/mg protein/minute, while the rate of metabolism in the lysate containing the human 1A2 P450 enzyme was not different from that in the control lysate. Therefore, the catalytic capabilities of orthologous P450 enzymes to activate 3MI cannot be extrapolated among different species. These results indicate that human P450s are capable of bioactivating 3MI to a metabolite which binds to cellular macromolecules suggesting that this compound may be toxic to humans.     

Superoxide and hydrogen peroxide in oxygen damage.

Escherichia coli were damaged and killed by exposure to hyperbaric oxygen. Lethality was measured as the decrease in the number of colonies formed upon plating the exposed cells onto rich agar. Damage was assessed by plating onto both rich and minimal agar. Cells which gave rise to visible colonies on rich but not on minimal agar were considered to be damaged. That this differential colony count was largely due to reparable damage rather than to stable mutagenesis was shown by replica plating from the rich onto the minimal agar. Most of the cells which had been unable to grow when directly plated onto minimal agar regained this ability after growth upon rich agar. Repair of the damage imposed by exposure to oxygen was thus more readily accomplished on a nutritionally rich medium. The enzymes superoxide dismutase, catalase, and peroxidase appeared to protect against oxygen damage. It is thus likely that both O₂^? and H₂O₂ are important agents of oxygen toxicity. In accord with this conclusion were the observations that augmented intracellular levels of these enzymes correlated with increased resistance towards oxygen damage, whereas increased respiratory capacity correlated with increased sensitivity towards hyperbaric oxygen.