Abundant Degradation Products Research Articles

Thermal degradation of diethanolamine at stripper condition for CO2 capture: Product types and reaction mechanisms

Amine-based absorption/stripping is one of the promising technology for CO2 capture from natural and industrial gas streams. During the process, amines and CO2 undergo irreversible reactions to produce undesired compounds, which cause corrosion, foaming, increased viscosity and breakdown of equipment, ultimately contributing to the economic loss and environmental pollution. In this study, the thermal degradation of aqueous diethanolamine in the presence and absence of dissolved CO2 was investigated. The experiments were performed in stainless steel cylinders. The results show that thermal degradation in the absence of CO2 was a slow process; triethanolamine, and tris(2-aminoethyl)amine were only the degradation products identified in the mixture In addition, the rate of degradation was very low, only 3% degradation was observed after 4 weeks. But in the presence of CO2, sixteen degradation products were identified, nine of which were new degradation products reported for the first time in this study. The 3-(2-hydroxyethyl)-2-oxazolidinone, 1,4-bis(2-hydroxyethyl)piperazine and triethanolamine were the most abundant degradation products. The remaining DEA concentration after 4 weeks was about 20% of the total amine concentration. The most probable degradation reactions and their mechanisms are also proposed.

Fate, Transformation, and Toxicological Impacts of Pharmaceutical and Personal Care Products in Surface Waters.

With the growth of the human population, a greater quantity of pharmaceutical and personal care products (PPCPs) have been released into the environment. Although research has addressed the levels and the impact of PPCPs in the environment, the fate of these compounds in surface waters is neither well known nor characterized. In the environment, PPCPs can undergo various transformations that are critically dependent on environmental factors such as solar radiation and the presence of soil particles. Given that the degradation products of PPCPs are poorly characterized, these “secondary residues” can be a significant environmental health hazard due to their drastically different toxicologic effects when compared with the parent compounds. To better understand the fate of PPCPs, we studied the degradation of selected PPCPs, including ibuprofen and clofibric acid, in aqueous solutions that contained kaolinite clay and were irradiated with a solar simulator. The most abundant degradation products were identified and assessed for their toxicologic impact on selected microorganisms. The degraded mixtures showed lower toxicity than the starting compounds; however, as these degradation products are capable of further transformation and interaction with other PPCPs in natural waters, our work highlights the importance of additionally characterizing the PPCP degradation products.

Ex vivo blood vessel bioreactor for analysis of the biodegradation of magnesium stent models with and without vessel wall integration.

Magnesium and its alloys are candidates for a new generation of biodegradable stent materials. However, the in vitro degradation of magnesium stents does not match the clinical degradation rates, corrupting the validity of conventional degradation tests. Here we report an ex vivo vascular bioreactor, which allows simulation of the microenvironment with and without blood vessel integration to study the biodegradation of magnesium implants in comparison with standard in vitro test conditions and with in vivo implantations. The bioreactor did simulate the corrosion of an intramural implant very well, but showed too high degradation for non-covered implants. It is concluded that this system is in between static incubation and animal experiments concerning the predictivity of the degradation.

Effects of biofumigation using Brassica juncea and Raphanus sativus in comparison to disinfection using Basamid on apple plant growth and soil microbial communities at three field sites with replant disease

The effects of biofumigation with Brassica juncea ‘Terra Plus’ and Raphanus sativus ‘Defender’ in comparison to Basamid on apple plant growth and on soil microbial communities were studied at three sites affected by replant disease under field conditions. Apple rootstocks were planted on differently treated plots to evaluate the effect of the treatments on plant growth under field and greenhouse conditions. The glucosinolates in biofumigant plant organs and their breakdown products in soils were determined. Denaturing gradient gel electrophoresis fingerprints were performed with 16S rRNA gene and ITS fragments amplified from total community DNA extracted from different soils. The highest glucosinolate concentrations were found in inflorescences of both biofumigant plant species with no differences between sites. The most abundant degradation product in soil biofumigated with B. juncea was 2-propenyl isothiocyanate, while in soil treated with R. sativus only 4-(methylthio)-3-butenyl isothiocyanate was detected. Effects of biofumigation were recorded to be stronger on fungi than on bacteria. Growth of apple rootstocks was positively affected by the treatments in a site-dependent manner. The effects of biofumigation evaluated by the apple plant growth were site-dependent and might result from suppression of soil-borne pests and pathogens, changes in soil microbial community compositions, and additional nutrients from the incorporated biomass.

Ionic liquid long-term stability assessment and its contribution to toxicity and biodegradation study of untreated and altered ionic liquids

In contrast to well understood degradation mechanisms in conventional lubricants generally promoted by thermo-oxidative stress, the degradation of ionic liquids is widely unknown although they are considered as promising novel types of lubricants. Hence, the ionic liquid long-term stability has been evaluated by small scale artificial alteration experiments under thermo-oxidative conditions. The ionic liquid selection was based on non-functionalized and functionalized ammonium type cations with three different counter anions. The identification of ionic liquid degradation products accomplished by high end mass spectrometric methods, namely time-of-flight/reflectron time-of-flight mass spectrometry and linear quadrupole trap-orbitrap-mass spectrometry, revealed that ionic liquids which were composed of functionalized cation moieties were prone to degradation. Furthermore, the amounts of the most abundant degradation product formed under various artificial alteration conditions have been quantified by ultra high pressure liquid chromatography coupled to electrospray ionization linear quadrupole ion trap orbitrap mass spectrometry, suggesting that the ionic liquid degradation preferably takes place at higher temperatures after a longer period of time. The proposed degradation mechanism requires the presence of nucleophilic species such as methanesulphonate anion. The (eco)toxicological impact of the selected ionic liquids have been evaluated by comprehensive toxicity studies and biodegradation experiments. As the evaluation of selected ionic liquids revealed contrary assessments from stability and (eco)toxicological studies, the need for mutual and complementary consideration of the ionic liquids for a successful implementation of ionic liquid lubricants has been disclosed.

Thermal Degradation Behavior and Product Speciation in Model Poly(dimethylsiloxane) Networks

The thermal degradation behavior of a series of well defined poly(dimethylsiloxane) (PDMS) model networks has been studied using a combination analytical thermal analysis techniques and multivariate statistical analysis in order to probe the influence of network architecture on degradation chemistry. The aim of this research has been to determine the effect differing network architectures: mono and bimodality, a range of crosslink density, inter-chain molar mass and percentage of free chain ends on the mechanisms of PDMS thermal degradation. A series of model PDMS networks have been formulated using of tin catalyzed condensation cure chemistry and a range of linear precursors to yield a matrix of model network systems. The thermal degradation chemistry of these model networks have been characterized in relation to their structure by means of pyrolysis gas chromatography mass spectrometry (Py-GCMS), thermal gravimetric analysis (TGA) and multivariate statistical analysis. The results clearly demonstrate that the structural architecture of (chemically similar) PDMS networks has a significant impact on the mechanisms of PDMS thermal degradation. Notability, with decreasing inter-crosslink chain length, larger cyclic siloxane species (>D5) become more abundant degradation products and that there is a relationship between inter-chain molar mass, degree of crosslinking and the thermal stability on the mechanisms of degradation. This work effectively demonstrates that quantifiable relationships exist between basic network architectures and the distributions of degradation derived species in PDMS networks.

The earthworm Eisenia fetida accelerates the removal of anthracene and 9, 10-anthraquinone, the most abundant degradation product, in soil

During biological degradation of anthracene, a polycyclic aromatic hydrocarbon often used as a model in biodegradation studies, intermediate products are formed that might be more persistent than anthracene. Earthworms have been used to remediate anthracene-contaminated soil, but few reports exists about dynamics of the most important intermediates formed. Anthracene-contaminated soil was amended with or without Eisenia fetida and degradation products monitored. A 41% removal of anthracene was found for treatments without earthworms and 93% for those with earthworms. Four degradation products were detected in soil with or without earthworms, of which 9, 10-anthraquinone was the most abundant. E. fetida accelerated the removal of 9, 10-anthraquinone compared to the soil without earthworms after 28 days. It was concluded that identical degradation products were detected in anthracene-contaminated soil, independent of the presence of E. fetida. The removal of anthracene and 9, 10-anthraquinone, the most abundant degradation product, however, was accelerated by E. fetida.

Degradation of leucomyosuppressin by enzymes in the hemolymph and midgut of Lacanobia oleracea and Spodoptera littoralis (Lepidoptera: Noctuidae) larvae

The degradation of 2 nmol synthetic leucomyosuppressin (LMS) by enzymes of the hemolymph, midgut lumen and midgut tissues of both Lacanobia oleracea and Spodoptera littoralis was investigated using reversed-phase high-performance liquid chromatography together with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Degradation of LMS in diluted hemolymph of L. oleracea and S. littoralis was not rapid, t 1/2 = 65.4 and 13.1 min, respectively, due to carboxypeptidase(s) and endopeptidase(s) present in the hemolymph. There was also some aminopeptidase activity in the hemolymph of both species. However, LMS was rapidly degraded by the diluted contents of the midgut lumen of L. oleracea and S. littoralis, t 1/2 = 0.5 and 2.2 min, respectively. The enzymes most likely responsible were trypsin-like serine protease(s) and carboxypeptidase(s). Degradation of LMS by midgut tissues containing 5 μg protein was not rapid in L. oleracea or S. littoralis, t 1/2 = 40.7 and 69.8 min, respectively. The most abundant degradation products probably resulted from carboxypeptidase activity, but some aminopeptidase activity was also detected.

Degradation products formed from long‐chain PUFA during deodorization of fish oil

AbstractOmega‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA) are sensitive to heat and may be destroyed by thermal processes such as deodorization. For example, deodorization of fish oil may induce polymerization, geometrical isomerization and cyclization of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. In this paper, we review our main findings on the effects of deodorization at three different temperatures on semi‐refined fish oil LC‐PUFA. Cyclic structures have been elucidated and mechanisms responsible for ring formation have been discussed. Polymers were found to be the most abundant degradation products formed during fish oil deodorization. A method for quantitative measurement of geometrical isomers of EPA and DHA by gas‐liquid chromatography (GLC) has been developed and validated. Overall assessment of the results obtained with this method suggests that deodorization at temperatures above 180°C affects the quality and the content of LC‐PUFA in fish oil.

Investigation on the thermal degradation of poly- n-alkyl acrylates and poly- n-alkyl methacrylates (C 1–C 12)

The thermal degradation of a series of poly- n-alkyl acrylates, from methyl to dodecyl, and poly- n-alkyl methacrylates, from butyl to nonyl, has been studied in isothermal conditions at 400–650 °C using pyrolysis-gas chromatography/mass spectrometry. The type and composition of the pyrolysis products gave useful information about the mechanism of thermal degradation. It was shown that the main thermal degradation processes for poly- n-alkyl acrylates are random main-chain scission with the formation of monomer, dimer, saturated diester, trimer, corresponding acetate and methacrylate, and non-radical side-chain reaction through six-member ring transition state. The most abundant degradation products coming from the alkyl ester decomposition are the corresponding olefin, aldehyde, and alcohol. Poly- n-alkyl methacrylates yield monomer as the predominant degradation product in all investigated pyrolysis conditions. Unlike poly(methyl methacrylate) which gives quantitative yields of monomer, however, the poly- n-alkyl methacrylates with longer alkyl chain produce also significant amounts of olefin and methacrylic acid.

Identification of degradants of a complex alkaloid using NMR cryoprobe technology and ACD/structure elucidator

AbstractIdentification of degradants of pharmaceuticals is a necessary challenge of the drug development process following the subjection of candidate molecules to a variety of physico‐chemical stresses. It would be desirable to be able to conduct such studies on a minimal amount of material. As a prototypical study, the isolation and identification of degradants of a sample of the complex indoloquinoline alkaloid, cryptospirolepine, was undertaken after prolonged storage in DMSO solution using a combination of cryogenic NMR probe technology and CASE (Computer‐Assisted Structure Elucidation) programs. None of the starting alkaloid remained after storage; a chromatogram of the DMSO solution demonstrated the presence of >25 components in the mixture. The two most abundant degradation products were identified as the known alkaloid cryptolepinone (∼35%) and an unprecedented rearrangement product, DP‐2, (∼16%).

Headspace solid‐phase microextraction with gas chromatography/mass spectrometry reveals a correlation between the degradation product pattern and changes in the mechanical properties during the thermooxidation of in‐plant recycled polyamide 6,6

AbstractThe increased susceptibility of in‐plant recycled polyamide 6,6 toward thermooxidation was shown by headspace solid‐phase microextraction with gas chromatography/mass spectrometry (HS‐SPME/GC‐MS), tensile testing, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). A correlation between the deterioration in mechanical properties and the formation of degradation products due to thermooxidation was found, and the most prominent decrease in mechanical properties coincided with the largest increase in the abundance of degradation products. The recycled materials had a shorter induction period toward oxidation, and their mechanical properties deteriorated faster than the mechanical properties of virgin material. The same trend was observed with HS‐SPME/GC‐MS because degradation products were found for recycled materials after oxidation times shorter than those for virgin material. Furthermore, larger amounts of degradation products were formed in the recycled materials. The high sensitivity of HS‐SPME/GC‐MS as an analytical tool was demonstrated because it was able to detect changes caused by oxidation considerably earlier than the other methods. Unlike DSC and FTIR, it could also show differences between samples recycled for different times. Four groups of degradation products—cyclic imides, pyridines, chain fragments, and cyclopentanones—were identified in thermooxidized polyamide 6,6. After 1200 h of thermooxidation, 1‐pentyl‐2,5‐pyrrolidinedione was the most abundant degradation product. Approximately four times more 1‐pentyl‐2,5‐pyrrolidinedione was formed in polyamide recycled three times than in virgin polyamide. Pyridines and chain fragments behaved toward oxidation and repeated processing like cyclic imides; that is, their amounts increased during oxidation, and larger amounts were formed in recycled materials than in virgin material. The cyclopentanone derivatives were present already in unaged material, and their amounts decreased during oxidation. Cyclopentanones were not formed because of the thermooxidation of polyamide 6,6. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3396–3407, 2002

The transfer of choline from the host to the bacterial cell surface requires glpQ in Haemophilus influenzae.

Haemophilus influenzae incorporates choline obtained from environmental sources onto its lipopolysaccharide as phosphorylcholine (ChoP). The decoration of the bacterial surface with ChoP contributes to pathogenesis by allowing for mimicry of the host. As the main reservoir for choline in the host is phosphatidylcholine, we tested whether other choline-containing molecules associated with eukaryotic membranes could provide an alternative source of choline. H. influenzae was able to use glycerophosphorylcholine (GPC), an abundant degradation product of phospholipids, as efficiently as free choline. Utilization of GPC required glpQ, which expresses an enzyme with glycerophosphodiester phosphodiesterase activity. In the absence of free choline, this gene was required for adherent H. influenzae to obtain choline directly from epithelial cells in culture. GlpQ therefore allows choline to be transferred from the host to the bacterial cell surface.

Occurrence of high concentrations of a unique degradation product of chlorophyll-a in particles residing below the thermocline throughout a period of oxygen depletion in Lake Kinneret

An unrecognized chlorophyllous pigment, designated Pheob4, was the most abundant degradation product of chlorophyll-a (Chla) in the hypolimimnion, benthic boundary layer and sedimenting particles in Lake Kinneret in June-July 1997, when a prolonged period of residual oxygen concentration was found below the thermocline. The highest concentration of Pheob4 was found in the benthic boundary layer, where it reached as high concentration as 2 μg l-1. In sediment traps positioned below the thermocline Pheob4 constituted from about 5 to 20% of the Chl-a concentration and in bottom sediments from 5 to 185%. Pheob4 was not detected in epilimnetic water samples, but was found in sediment traps located within the oxygenated water column, within the range of surface wave action. Comparison of regular traps, with traps poisoned by formaldehyde indicates that the importance of Pheob4- containing particles in the sedimentation flux is relatively low, and that the bulk of Pheob4 found in the bottom sediment is apparently a result of Chl-a transformation in situ by biological activity. The timing and location of Pheob4 appearance coincided with the lake compartments where denitrification apparently took place. This suggests that Pheob4 may be used as a target pigment to trace organic matter processing under transient conditions in the water column and on the bottom sediments. Pheob4 was tentatively identified as 132, 172 cyclophaeophorbide-a enol. But, since the identification was done on a different system than the one used for the analysis of most of the samples, further investigation is required to verify that finding.

CYCLOPHEOPHORBIDE A IN SUSPENDED PARTICLES IN THE META‐ AND HYPOLIMNION DURING OXYGEN DEPLETION IN A SUBTROPICAL LAKE

Ostrovsky, I. & Yacobi, Y. Z.Israel Oceanographic and Limnological Research, Kinneret Limnological Laboratory, P.O. Box 345, Tiberias 1402, IsraelCyclopheophorbide a (CPP) was the most abundant degradation product of chlorophyll a (Chl a) in the hypolimimnion, benthic boundary layer and sedimenting particles in Lake Kinneret in June‐July 1997, when a prolonged period of residual oxygen concentration was found below the thermocline. The highest concentration of CPP was found in the benthic boundary layer, where it reached as high a concentration as 2 *g liter‐1. In sediment traps positioned below the thermocline CPP constituted from about 5 to 20% of the Chl a concentration and in bottom sediments from 5 to 185%. CPP was not detected in epilimnetic water samples, but was found in sediment traps located within the oxygenated water column, within the range of surface wave action. Comparison of regular traps, with traps poisoned by formaldehyde indicates that the importance of CPP‐containing particles in the sedimentation flux is relatively low, and that the bulk of CPP found in the bottom sediment is apparently a result of Chl a transformation in situ by biological activity. The timing and location of CPP appearance coincided with the lake compartments where denitrification apparently took place. This suggests that CPP can be used as a target pigment to trace organic matter processing under transient conditions in the water column and on the bottom sediments.

Study of electron beam irradiation effects on 2,4,6-trichloroanisole as a contaminant of cork by gas chromatography-mass spectrometry

The effects of electron beam irradiation on solutions of 2,4,6-trichloroanisole (TCA), the major contributor to sensory defects in cork stoppers, were studied at different doses (25 and 50 kGy) by qualitative and quantitative analysis of its breakdown products. The behaviour of irradiated TCA was also evaluated in the presence of cork. Analyses were performed by gas chromatography-mass spectrometry (GC-MS). Irradiation of TCA caused the formation of 2-chloroanisole, 4-chloroanisole, 2,4-dichloroanisole and 2,6-dichloroanisole. Quantitative data showed that the amount of TCA decreases with increasing dose of irradiation, whereas higher concentrations of all its derivatives, except for 2,6-trichloroanisole, were found in samples irradiated with a 50 kGy dose. Among the radiolytic products of TCA, 2,4-dichloroanisole and 4-chloroanisole were found to be the most abundant degradation products. Irradiation of cork contaminated by TCA could positively affect cork quality both from organoleptic and sanitary points of view, since the chlorinated anisoles found in irradiated solutions give less off-odours than TCA and since they are not listed under the EPA hazardous substances.

The antibiotic and anticancer active aurein peptides from the Australian Bell Frogs Litoria aurea and Litoria raniformis the solution structure of aurein 1.2.

Seventeen aurein peptides are present in the secretion from the granular dorsal glands of the Green and Golden Bell Frog Litoria aurea, and 16 from the corresponding secretion of the related Southern Bell Frog L. raniformis. Ten of these peptides are common to both species. Thirteen of the aurein peptides show wide-spectrum antibiotic and anticancer activity. These peptides are named in three groups (aureins 1-3) according to their sequences. Amongst the more active peptides are aurein 1.2 (GLFDIIKKIAESF-NH2), aurein 2.2 (GLFDIVKKVVGALGSL-NH2) and aurein 3.1 (GLFDIVKKIAGHIAGSI-NH2). Both L. aurea and L. raniformis have endoproteases that deactivate the major membrane-active aurein peptides by removing residues from both the N- and C-termini of the peptides. The most abundant degradation products have two residues missing from the N-terminal end of the peptide. The solution structure of the basic peptide, aurein 1.2, has been determined by NMR spectroscopy to be an amphipathic alpha-helix with well-defined hydrophilic and hydrophobic regions. Certain of the aurein peptides (e.g. aureins 1.2 and 3.1) show anticancer activity in the NCI test regime, with LC50 values in the 10-5-10-4 M range. The aurein 1 peptides have only 13 amino-acid residues: these are the smallest antibiotic and anticancer active peptides yet reported from an anuran. The longer aurein 4 and 5 peptides, e.g. aurein 4.1 (GLIQTIKEKLKELAGGLVTGIQS-OH) and aurein 5. 1 (GLLDIVTGLLGNLIVDVLKPKTPAS-OH) show neither antibacterial nor anticancer activity.

Enzymatic oxidative activity in sardine ( Sardina pilchardus ) and herring ( Clupea harengus ) during chilling and correlation with quality

Enzymatic oxidative activity of two fatty fish species, sardine (Sardina pilchardus) and herring (Clupea harengus), was studied during chilled storage. Lipoxygenase enzyme activity was isolated and tested by measuring the hydroperoxides produced after induced oxidation of arachidonic and docosahexaenoic fatty acids. The most abundant degradation products of the hydroperoxides formed were 12- and 16-hydroxy acids which were detected by HPLC. Lipoxygenases were concentrated in the skin tissue of fish, and were active for up to 48 h of chilled storage. The pro-oxidative activity due to haem proteins continued for longer than that due to lipoxygenase. Trends of fluorescent formation resulting from interaction between oxidation products and biological amino constituents were compared with the pro-oxidative activities to establish correlations with quality loss during chilling.

Matrix metalloproteinase digestion of aggrecan in human cartilage tumours

Substantial experimental and clinical evidence suggests that the catabolism of extracellular matrix components is a prerequisite for invasive and metastatic behaviour of solid tumours. Chondrosarcomas are malignant cartilaginous tumours that most commonly arise in bone, and the large aggregating proteoglycan aggrecan is a major component of the extracellular matrix of these tumours. Matrix metalloproteinases (MMPs) have been implicated in tumour invasiveness. The purpose of this study was to determine whether MMPs play a role in aggrecan catabolism in cartilage tumours. In order to detect aggrecan digestion products resulting from in vivo cleavage at the MMP site, protein extracts from human articular cartilage and from various cartilage tumours were analysed by Western blot using an antibody to the FVDIPEN neoepitope generated by MMP cleavage. Examination of cartilage extracts revealed a trend of increasing aggrecan digestion at the MMP site with age. One hyaline chondrosarcoma and three osteochondromas lacked detectable aggrecan fragments with the carboxy terminal FVDIPEN neoepitope. Two osteochondromas gave weak signals. However, all chondrosarcomas with degenerating extracellular matrix or with a myxoid component exhibited strong FVDIPEN immunoreactivity. These results demonstrate that, in contrast to the benign cartilage tumour osteochondroma, human chondrosarcomas contain abundant aggrecan degradation products resulting from cleavage in vivo at the MMP site in the interglobular domain. These data support the concept that MMPs participate in the degradation of extracellular matrix in chondrosarcoma, allowing the neoplastic chondrocytes to escape local confinement, migrate, and invade neighbouring and remote tissues.

Characterization of the Interactions of Plasminogen and Tissue and Vampire Bat Plasminogen Activators with Fibrinogen, Fibrin, and the Complex of d-Dimer Noncovalently Linked to Fragment E

Vampire bat plasminogen activator (b-PA) causes less fibrinogen (Fg) consumption than tissue-type plasminogen activator (t-PA). Herein, we demonstrate that this occurs because the complex of D-dimer noncovalently linked to fragment E ((DD)E), the most abundant degradation product of cross-linked fibrin, as well as Fg, stimulate plasminogen (Pg) activation by t-PA more than b-PA. To explain these findings, we characterized the interactions of t-PA, b-PA, Lys-Pg, and Glu-Pg with Fg and (DD)E using right angle light scattering spectroscopy. In addition, interactions with fibrin were determined by clotting Fg in the presence of various amounts of t-PA, b-PA, Lys-Pg, or Glu-Pg and quantifying unbound material in the supernatant after centrifugation. Glu-Pg and Lys-Pg bind fibrin with Kd values of 13 and 0.13 microM, respectively. t-PA binds fibrin through two classes of sites with Kd values of 0.05 and 2.6 microM, respectively. The second kringle (K2) of t-PA mediates the low affinity binding that is eliminated with epsilon-amino-n-caproic acid. In contrast, b-PA binds fibrin through a single kringle-independent site with a Kd of 0.15 microM. t-PA competes with b-PA for fibrin binding, indicating that both activators share the same finger-dependent site on fibrin. Glu-Pg binds (DD)E with a Kd of 5.4 microM. Lys-Pg binds to (DD)E and Fg with Kd values of 0.03 and 0.23 microM, respectively. t-PA binds to (DD)E and Fg with Kd values of 0.02 and 0.76 microM, respectively; interactions were eliminated with epsilon-amino-n-caproic acid, consistent with K2-dependent binding. Because it lacks a K2-domain, b-PA does not bind to either (DD)E or Fg, thereby explaining why b-PA is more fibrin-specific than t-PA.