A branched monomethoxypoly(ethylene glycol) for protein modification

Procedures are described for linking monomethoxypoly(ethylene glycol) (mPEG) to both epsilon and alpha amino groups of lysine. The lysine carboxyl group can then be activated as a succinimidyl ester to obtain a new mPEG derivative (mPEG2-COOSu) with improved properties for biotechnical applications. This branched reagent showed in some cases a lower reactivity toward protein amino groups than the linear mPEG from which it was derived. A comparison of mPEG- and mPEG2-modified enzymes (ribonuclease, catalase, asparaginase, trypsin) was carried out for activity, pH and temperature stability, Km and Kcat values, and protection to proteolytic digestion. Most of the adducts from mPEG and mPEG2 modification presented similar activity and stability toward temperature change and pH change, although in a few cases mPEG2 modification was found to increase temperature stability and to widen the range of pH stability of the adducts. On the other hand, all of the enzymes modified with the branched polymer presented greater stability to proteolytic digestion relative to those modified with the linear mPEG. A further advantage of this branched mPEG lies in the possibility of a precise evaluation of the number of polymer molecules bound to the proteins; upon acid hydrolysis, each molecule of mPEG2 releases a molecule of lysine which can be detected by amino acid analysis. Finally, dimerization of mPEG by coupling to lysine provides a needed route to monofunctional PEGs of high molecular weight.

Preparation of characterization of poly(ethylene glycol) vinyl sulfone

Synthesis of the vinyl sulfone and chloroethyl sulfone derivatives of poly(ethylene glycol) (PEG) is described. The chloroethyl sulfone (CES-PEG) is rapidly converted to the vinyl sulfone (VS-PEG) in the presence of base but is stable in water at neutral pH. Reactions with small molecules such as beta-mercaptoethanol and N alpha-acetyllysine show that the vinyl sulfone derivative is highly selective for reaction with sulfhydryl groups relative to reaction with amino groups. Also, VS-PEG is stable in water. These properties indicate that VS-PEG should be useful for selective attachment of PEG to protein cysteine groups. This hypothesis was verified by reacting VS-PEG with cysteine groups of reduced ribonuclease (RNase); the reaction is rapid and selective at pH 7-9. Reaction at lysine sites of unreduced RNase occurs slowly at pH 9.3 and is essentially complete after 100 h. Amino acid residues other than lysine and cysteine are not reactive toward VS-PEG. The covalent linkage between VS-PEG and lysine or cysteine groups is shown to be stable.

Bioconjugation in pharmaceutical chemistry

Polymer conjugation is of increasing interest in pharmaceutical chemistry for delivering drugs of simple structure or complex compounds such peptides, enzymes and oligonucleotides. For long time drugs, mainly with antitumoral activity, have been coupled to natural or synthetic polymers with the purpose of increasing their blood permanence time, taking advantage of the increased mass that reduces kidney ultrafiltration. However only recently complex constructs were devised that exploit the 'enhanced permeability and retention' (EPR) effect for an efficient tumor targeting, the high molecular weight for adsorption or receptor mediated endocytosis and finally a lysosomotropic targeting, taking advantage of acid labile bonds or cathepsin susceptible polypeptide spacers between polymer and drug. New original, very active conjugates of this type, as those based on poly(hydroxyacrylate) polymers, are already in advanced state of development. Labile oligonucleotides, including antisense drugs, were also successfully coupled to polymers in view of an increased cell penetration and stabilization towards nucleases. However, the most active research activity resides in the field of polypeptides and proteins delivery, mainly for the two following reasons: first of all because a great number of therapeutically interesting compounds are now being produced by genetic engineering in large quantity and, secondly, because these products are difficult to administer to patients for several inherent drawbacks. Proteins are in fact easily digested by many endo- and exo-peptidases present in blood or in other body districts; most of them are immunogenic to some extent and, finally, they are rapidly excreted by kidney ultrafiltration. Covalent polymer conjugation at protein surface was demonstrated to reduce or eliminate these problems, since the bound polymer behaves like a shield hindering the approach of proteolytic enzymes, antibodies, or antigen processing cell. Furthermore, the increase of the molecular weight of the conjugate allows to overcome the kidney elimination threshold. Many successful results were already obtained in peptides and proteins, conjugated mainly to water soluble or amphiphilic polymers like poly(ethylene glycol) (PEG), dextrans, or styrenemaleic acid anhydride. Among the most successful are the conjugates of asparaginase, interleukin-2 or -6 and neocarcinostatin, to remind some antitumor agents, adenosine deaminase employed in a genetic desease treatment, superoxide dismutase as scavenger of toxic radicals, hemoglobin as oxygen carrier and urokinase and streptokinase as proteins with antithrombotic activity. In pharmaceutical chemistry the conjugation with polymers is also of great importance for synthetic applications since many enzymes without loss of catalytic activity become soluble in organic solvents where many drug precursors are. The various and often difficult chemical problems encountered in conjugation of so many different products prompted the development of many synthetic procedures, all characterized by high specificity and mild condition of reaction, now known as 'bioconjugation chemistry'. Bioconjugation developed also the design of new tailor-made polymers with the wanted molecular weight, shape, structure and with the functional groups needed for coupling at the wanted positions in the chain.

Doppler echocardiographic evaluation of pulmonary artery pressure in chronic obstructive pulmonary disease. A European multicentre study. Working Group on Noninvasive Evaluation of Pulmonary Artery Pressure. European Office of the World Health Organization, Copenhagen

The feasibility, reproducibility and reliability of Doppler echocardiography in evaluation of pulmonary artery pressure in patients with chronic obstructive pulmonary disease (COPD) were determined in a multicentre study. In 100 COPD patients with mean pulmonary artery pressure ranging from 10 to 62 mmHg at cardiac catheterization, pulmonary pressure estimation was attempted by four Doppler echocardiographic methods. These methods comprised the calculation of transtricuspid and transpulmonary pressure gradients from Doppler-detected tricuspid or pulmonary regurgitation, the evaluation of right ventricular outflow tract velocity profiles with the measurement of right ventricular systolic time intervals and the measurement of the right ventricular isovolumic relaxation time. In 98 (98%) patients at least one of the methods could be employed. A tricuspid regurgitation jet was detected in 47 (47%) patients but its quality was adequate for measurement in 30 (30%). Pulmonary regurgitation jet velocity was measured only in five cases. The standard error of estimate in testing intra- and interobserver reproducibility of Doppler systolic time intervals was less than 5%. The predictive value of right ventricular outflow tract acceleration time less than 90 ms in the identification of patients with mean pulmonary artery pressure greater than 20 mmHg was 80%. Of Doppler echocardiographic data, best correlations with mean pulmonary artery pressure were found for the transtricupid gradient (r = 0.73, SEE = 7.4 mmHg), for the right ventricular acceleration time (r = 0.65, SEE = 8 mmHg) and right ventricular isovolumic relaxation time (r = 0.61, SEE = 8.5 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence and prognostic significance of right-sided cardiac mobile thrombi in acute massive pulmonary embolism

The prevalence of right-sided cardiac mobile thrombi, "in transit" from the systemic venous system, was 18% in a series of 130 patients with massive pulmonary embolism referred to early echocardiography and receiving thrombolytic drugs (56%) or intravenous heparin (40%). The mortality rate was lower than previously reported and seemed to be related more to clinical and hemodynamic impairment than to presence of thromboembolus.

Opposite hemispheric activations as a result of emotionally threatening and non-threatening words

Twenty right-handed males participated in a tachistoscopic unilateral letter recognition task with three conditions. In the control condition, each trial consisted of three consonants that were flashed horizontally to the left or to the right visual field. In the threat and non-threat conditions, each lateral three-letter presentation was preceded by an emotionally threatening or non-threatening word presented in central fixation. Across conditions, subjects identified more letters correctly in the right visual field than in the left visual field. The concurrent presentation of threatening words resulted in a selective enhancement of left visual-field performances. The concurrent presentation of non-threatening words resulted in a selective right visual-field enhancement. Our conclusion is that threatening stimuli prime the right hemisphere and can alter predicted laterality patterns.

N-hydroxysuccinimide carbonates and carbamates are useful reactive reagents for coupling ligands to lysines on proteins

Ligands containing amino or hydroxyl groups were converted to their corresponding activated N-hydroxysuccinimidyl carbamate and carbonate by reaction with disuccinimidyl carbonate (DSC). The latter reagents can be used for the group-specific modification of primary amines as an alternative to the widespread usage of N-hydroxysuccinimide esters. Biotin and 2,4-dinitrophenyl (DNP) derivatives were used as examples to demonstrate the approach. Biotin and DNP were each extended by attaching two different spacer arms, carrying either a hydroxyl group or a primary amine as terminal functions. The latter were then activated via their conversion to N-hydroxysuccinimide carbonates and carbamates, respectively. The usefulness of these reagents for protein modification was investigated. The modified proteins obtained exhibited similar stability and activity characteristics compared to those modified with active N-hydroxysuccinimdyl esters. The activation of hydroxy- or amino-terminating compounds with DSC represents a general method that can be applied to any ligand which contains these functional groups for its covalent coupling to amines.

The spectrum of pulmonary embolism. Clinicopathologic correlations

Pulmonary embolism (PE) is still underdiagnosed even in hospitalized patients. In our recent experience, out of 92 postmortem cases of massive or submassive PE, only 28% were diagnosed before death, whereas the false-positives accounted only for 3% of cases. Similar conclusions have been drawn from large-scale autopsy studies performed in Norway and in the United States. The most important causes of an incorrect diagnosis are failure to suspect PE, and the protean nature of the disease. Remarkable differences actually exist concerning the point of origin and the final localization, as well as the size and age of thromboemboli, the presence or absence of pulmonary infarction, and the underlying pathology. Often a fatal embolus is relatively small but hardly tolerated because of the underlying cardiopulmonary situation. Attention should be called to the frequent autopsy finding of multiple PEs and pulmonary infarctions of apparently different age. This finding is important since it indicates that these patients suffered successive embolizations and the eventual death might have been prevented if an early diagnosis had been made.

The varying evolution of Friedreich's ataxia cardiomyopathy

During a mean follow-up period of 8 years, 17% of 66 patients with Friedreich's ataxia developed hypokinetic-dilated cardiomyopathy; most patients originally had a hypertrophic left ventricle. The presence of pathologic Q waves identifies a subgroup of patients with wall motion abnormalities; these patients are more likely to develop a hypokinetic left ventricle, and the prognosis is ostensibly poorer.

Bisphosphonate complexation and calcium doping in silica xerogels as a combined strategy for local and controlled release of active platinum antitumor compounds

The production of bone substitute biomimetic materials which could also act as antitumoral drug release agents is of enormous interest. We report in this paper the synthesis and characterization of a novel platinum dinuclear complex containing a geminal bisphosphonate and its embodiment into xerogels prepared by the sol-gel method. Our goal was to obtain a hybrid inorganic matrix that could release a platinum species active against bone tumors or metastases, upon local implant. Two silica xerogels were considered: one was composed of pure silica, while the other contained also some calcium as potential release-modulating agent thanks to its high affinity for bisphophonates. The platinum-complex loading capacity of the inorganic matrices, the release kinetics in buffer simulating physiological conditions, and the stability upon storage were investigated as a function of Pt-complex concentration and calcium addition. We found that the presence of calcium in the composites deeply influences not only the stability of the formulations but also the nature of the platinum complex liberated in solution.

Wet sol–gel derived silica for controlled release of proteins

The potential of wet sol-gel derived silica gels as new matrices for the entrapment and sustained release of proteins was investigated. Model proteins, BSA, ribonuclease-A and avidin, with differing molecular weights and/or isoelectric points, were entrapped in two silica polymer formulations having different silica contents (4% and 12% wt/v). The conformational stability of the proteins after entrapment and their release after immersion into physiological conditions were measured. Circular dichroism analysis showed that protein conformation is maintained after entrapment and stability is enhanced. Protein-free formulations were injected intramuscularly into BALB/c mice to monitor the in vivo fate of the matrix, and the results showed that the gel is totally reabsorbed, without any apparent surrounding inflammation process. The time required for matrix bioerosion varied between one to three weeks, depending on its SiO(2) content. Erosion was also measured in vitro and the contribution of erosion and diffusion to the release of the embedded proteins was quantified. These data indicate that wet silica polymers obtained by the sol-gel route are promising matrices for the sustained release of protein drugs.

A single-step photolithographic interface for cell-free gene expression and active biochips

We have developed a biochip platform technology suitable for controlled cell-free gene expression at the micrometer scale. A new hybrid molecule, "Daisy", was designed and synthesized to form in a single step a biocompatible lithographic interface on silicon dioxide. A protocol is described for the immobilization of linear DNA molecules thousands of base pairs long on Daisy-coated surfaces with submicrometer spatial resolution and up to high densities. On-chip protein synthesis can be obtained with a dynamic range of up to four orders of magnitude and minimal nonspecific activity. En route to on-chip artificial gene circuits, a simple two-stage gene cascade was built, in which the protein synthesized at the first location diffuses to regulate the synthesis of another protein at a second location. We demonstrate the capture of proteins from crude extract onto micrometer-scale designated traps, an important step for the formation of miniaturized self-assembled protein chips. Our biochip platform can be combined with elastomeric microfluidic devices, thereby opening possibilities for isolated and confined reaction chambers and artificial cells in which the transport of products and reagents is done by diffusion and flow. The Daisy molecule and described approach enables groups not proficient in surface chemistry to construct active biochips based on cell-free gene expression.

DNA condensation by high-affinity interaction with avidin

Avidin, the basic biotin-binding glycoprotein from chicken egg white, is known to interact with DNA, whereas streptavidin, its neutral non-glycosylated bacterial analog, does not. In the present study we investigated the DNA-binding properties of avidin. Its affinity for DNA in the presence and absence of biotin was compared with that of other positively charged molecules, namely the protein lysozyme, the cationic polymers polylysine and polyarginine and an avidin derivative with higher isoelectric point (pI approximately 11) in which most of the lysine residues were converted to homoarginines. Gel-shift assays, transmission electron microscopy and dynamic light scattering experiments demonstrated an unexpectedly strong interaction between avidin and DNA. The most pronounced gel-shift retardation occurred with the avidin-biotin complex, followed by avidin alone and then guanidylated avidin. Furthermore, ultrastructural and light-scattering studies showed that avidin assembles on the DNA molecule in an organized manner. The assembly leads to the formation of nanoparticles that are about 50-100 nm in size (DNA approximately 5 kb) and have a rod-like or toroidal shape. In these particles the DNA is highly condensed and one avidin is bound to each 18 +/- 4 DNA base pairs. The complexes are very stable even at high dilution ([DNA] =10 pM) and are not disrupted in the presence of buffers or salt (up to 200 mM NaCl). The other positively charged molecules also condense DNA and form particles with a globular shape. However, in this case, these particles disassemble by dilution or in the presence of low salt concentration. The results indicate that the interaction of avidin with DNA may also occur under physiological conditions, further enhanced by the presence of biotin. This DNA-binding property of avidin may thus shed light on a potentially new physiological role for the protein in its natural environment.

Dexamethasone Conjugation to Biodegradable Avidin-Nucleic-Acid-Nano-Assemblies Promotes Selective Liver Targeting and Improves Therapeutic Efficacy in an Autoimmune Hepatitis Murine Model

Steroids are the standard therapy for autoimmune hepatitis (AIH) but the long-lasting administration is hampered by severe side effects. Methods to improve the tropism of the drug toward the liver are therefore required. Among them, conjugation to nanoparticles represents one possible strategy. In this study, we exploited the natural liver tropism of Avidin-Nucleic-Acid-Nano-Assemblies (ANANAS) to carry dexamethasone selectively to the liver in an AIH animal model. An acid-labile biotin-hydrazone linker was developed for reversible dexamethasone loading onto ANANAS. The biodistribution, pharmacokinetics and efficacy of free and ANANAS-linked dexamethasone (ANANAS-Hz-Dex) in healthy and AIH mice were investigated upon intraperitoneal administration. In ANANAS-treated animals, the free drug was detected only in the liver. Super-resolution microscopy showed that nanoparticles segregate inside lysosomes of liver immunocompetent cells, mainly involved in AIH progression. In agreement with these observational results, chronic low-dose treatment with ANANAS-Hz-Dex reduced the expression of liver inflammation markers and, in contrast to the free drug, also the levels of circulating AIH-specific autoantibodies. These data suggest that the ANANAS carrier attenuates AIH-related liver damage without drug accumulation in off-site tissues. The safety and biodegradability of the ANANAS carrier make this formulation a promising tool for the treatment of autoimmune liver disorders.

In vitro and in vivo evaluation of acellular diaphragmatic matrices seeded with muscle precursors cells and coated with VEGF silica gels to repair muscle defect of the diaphragm

In this work, a bioartificial system consisting of VEGF-loaded porous silica gel and myoblasts cultured on acellular diaphragmatic matrix (ADM) has been implanted to repair a surgically created diaphragmatic defect in Lewis rats. ADMs exerted a strong angiogenic response on chorio-allantoic membrane. Cytotoxicity, VEGF release and matrix erodibility in vitro tests demonstrated that the silica support was nontoxic and that the VEGF bioactivity was maintained after matrix entrapment and it was released within a timeframe that can be modulated by synthesis parameters. Different grafts composed by ADMs with and without autologous male myoblasts or/and VEGF-loaded porous silica gel have been implanted to repair previously created diaphragmatic defects in female Lewis rats. Patches composed of ADMs and myoblasts appeared well preserved until 8 weeks, and contained multinucleated cells and cholinergic fibers. At 8 weeks, the implanted cells were still present inside the patches. The disappointing results obtained when VEGF was delivered by porous silica gel were probably due to an abnormal angiogenic response following an excess of local growth factor concentration. Taken together, these results confirmed that our matrices contained biologically active angiogenic factors which were per se sufficient to induce neo-vessels formation, thus allowing the survival of implanted myoblasts.

fac-{Ru(CO)3}2+-Core Complexes and Design of Metal-Based Drugs. Synthesis, Structure, and Reactivity of Ru−Thiazole Derivative with Serum Proteins and Absorption−Release Studies with Acryloyl and Silica Hydrogels as Carriers in Physiological Media

The reaction of [Ru2(CO)6Cl4], 1, with excess THZ (1,3-thiazole) in absolute ethanol at 55 degrees C produces fac-[Ru(CO)3Cl2(THZ)], 2, in high yield. [Ru(CO)2Cl2(THZ)2], 3, is formed at higher temperature (ca 70 degrees C) and higher concentration of THZ. The X-ray structures of the new compounds have been determined, and density functional studies performed at the hybrid B3LYP/(Lanl2DZ, Ru; 6-311+G**, CHClNOS) level allowed the estimation of the structures of several conformers as well as that of their relative total electronic energies. Compound 2 is soluble (slowly) in aqueous media, where it reacts with the transport proteins bovine serum albumin (BSA) and human apotransferrin (HTF), and at a lower extent with calf thymus DNA (CT-DNA) and with guanosine-5'-monophosphate (GMP). The complex molecule is adsorbed by certain synthetic acryloyl polymers that have terminal carboxylate functions and is embedded in silica gels when these latter are prepared in the presence of a solution of 2. Ruthenium species are slowly released from the loaded gels into physiological solutions at pH 7.4. The reactivity of 2 with biomolecules and synthetic hydrogels makes it a compound of interest for anticancer and antimetastases tests.

In vivo fate of avidin-nucleic acid nanoassemblies as multifunctional diagnostic tools

This study describes the formulation optimization and body-cell distribution and clearance in mice of a dually fluorescent biodegradable poly avidin nanoassembly based on the novel Avidin-Nucleic-Acid-Nano-ASsembly (ANANAS) platform as a potential advancement of classic avidin/biotin-based targeted delivery. The nanoformulation circulates freely in the bloodstream; it is slowly captured by filter organs; it is efficiently cleared within 24-48 h, and it is poorly immunogenic. The system displays more favorable properties than its parent monomeric avidin and it is a promising tool for diagnostic purposes for future translational aims, for which free circulation in the bloodstream, safety, multifunctionality and high composition definition are all necessary requirements. In addition, the assembly shows a time-dependent cell penetration capability, suggesting it may also function as a NP-dependent drug delivery tool. The ease of preparation together with the possibility to fine-tune the surface composition makes it also an ideal candidate to understand if and how nanoparticle composition affects its localization.

Silica xerogels as a delivery system for the controlled release of different molecular weight heparins

In this work, we investigated a sol-gel derived silica matrix as a delivery system for the prolonged release of different molecular weight heparins, which allows the glycosaminoglicons to retain their whole biological activity. Several xerogels were obtained by embedding different molecular weight heparins into matrices prepared by using different amount of NH4OH as a catalyst during gel formation. Gel synthesis parameters, drug release properties, and xerogels surface area were evaluated. Unfractionated, low and oligo-molecular weight heparins were embedded into xerogels and the effect of the molecular weight on the release kinetics and the retained biological activity has been investigated. The results show that the surface area of the matrix is a determinant parameter affecting drug release kinetics. This structural feature can be modified by varying the catalyst tetraethoxysilane molar ratio used during the matrix synthesis. In most cases release kinetics fitted the Higuchi diffusive model and a lower diffusion rate was observed from silica matrices characterized by a smaller surface area. In the case of matrices with lower surface area, loaded with unfractionated heparin, zero order kinetics was observed. In this paper, we have defined a heparin release silica xerogel system and we have pointed out how modulation of its synthesis parameters allows adjusting the release of heparin according to therapeutic needs.

Protective effect of superoxide dismutase and polyethylene glycol-linked superoxide dismutase against renal warm ischemia/reperfusion injury

The protective effect of oxygen free radical scavenger superoxide dismutase (SOD) against the warm ischemic damage that occurs in kidneys harvested from non-heart-beating donors is controversial because of its short half-life. In this model, we compared the protective effect of SOD and two longer lasting polyethylene glycol (PEG)-linked forms of SOD in a model of renal ischemia induced by 60 min of arterial clamping in rats. Rats treated with PEG1-SOD and PEG2-SOD had a better renal function than controls, with significantly lower serum creatinine levels throughout the follow-up period and a significantly higher creatinine clearance on postoperative days 1, 2, and 4. In native SOD treated-rats, serum creatinine was lower than in controls, though not significantly so, and creatinine clearance was significantly higher on postoperative day 4. Our results indicate that the protective effect of SOD against renal warm ischemia can be enhanced by prolonging its half-life by binding the enzyme to PEG.

The effect of Na(2)CO(3), NaF and NH(4)OH on the stability and release behavior of sol-gel derived silica xerogels embedded with bioactive compounds

Stability, defined as the reproducible behavior of a device upon its storage, is an important issue in pharmaceutical formulation. Silica xerogels obtained through the sol-gel route are relatively new as matrices for the controlled release of drugs. In some cases, it was observed that their behavior changes upon storage, so that they cannot always be defined as "stable". This occurs especially when gel processing is performed at mild temperatures, a procedure that may have to be used to prevent degradation of the embedded drug. This work investigated the use of inorganic catalysts as potential xerogel stability inducers when gel curing by heating is not applicable. Three compounds known to accelerate sol-gel polymerization, namely ammonia, sodium fluoride and sodium carbonate, were introduced during the polymerization of low-temperature processed inorganic and organically modified gels, and the effect of each compound on xerogel stability and drug release was monitored. The use of carbonate leads to formulations with good retention properties, as opposed to ammonia and NaF, which lead to poorly retentive xerogels in accordance with their known ability to increase porosity. Ammonia was shown to be a poor stability promoter independently of gel composition, as opposed to fluoride and carbonate, which both displayed stabilizing properties in a dose-dependent manner. No correlation was found between xerogel stability and drug release properties. An attempt was also made to correlate stability data with polymerization rates and wet gel syneresis time evolution with the purpose of identifying one or more synthesis parameters that could act as stability predictors for pre-formulation studies. No correlation was found between stability and syneresis data. A similar trend in the curve of gel time vs. catalyst concentration was observed for the two stabilizing catalysts, which was different for the non-stabilizing ammonia. It was concluded that the trend of this curve could potentially provide an indicator of catalyst stabilizing efficacy.

Selective alkylation and acylation of alpha and epsilon amino groups with PEG in a somatostatin analogue: tailored chemistry for optimized bioconjugates

The effects of the type and location of polymer grafting on the biological activity of different mono-PEG derivatives of the somatostatin analogue RC160 were evaluated. A chemical strategy to obtain mono-PEG alkylation or acylation of the peptide's alpha-terminal or lysil-epsilon primary amines was devised. Selective BOC protection of the two available primary amines, followed by reaction with two different PEG reagents and removal of the protecting group, was carried out. Chemical characterization, structural studies, and the evaluation of the biological activity of the bioconjugates synthesized allowed the identification of the one having characteristics more suitable for therapeutic application. This corresponds to the mono-epsilon-lysil-pegylated form, obtained by reductive alkylation, where the amine's positive charge is preserved. The results obtained suggest the importance of preliminary studies in the development of new polymer-peptide conjugates with improved pharmacological properties.

A labeling, detection, and purification system based on 4-hydroxyazobenzene-2-carboxylic acid: an extension of the avidin-biotin system

We introduce a new nonradioactive, chromogenic label based on 4-hydroxyazobenzene-2-carboxylic acid (HABA), which is suitable for bioanalytical application, e.g., detection, localization, isolation, and purification. The HABA label is superior to other systems where it is difficult to separate labeled from unlabeled molecules or to determine the amount of label. HABA is readily detected spectroscopically by its absorption at 350 nm or by its interaction with avidin that results in a red shift to 500 nm. The HABA reagents described can be conjugated to a variety of functional groups on biomolecules and purified thereafter by affinity chromatography on an avidin column. The interaction of the HABAylated biomolecules with their corresponding targets is detected with high-affinity anti-HABA antibodies or with avidin. The nonradioactive, chromogenic HABA-based reagents form a homogeneous system that can complement or replace systems where facile quantification of the label is desired.

Role of echo/Doppler in the diagnosis of pulmonary embolism

Echocardiography supplemented with pulsed and continuous wave Doppler facilities is a potent diagnostic tool in many cardiovascular disorders. Its potential role in the management of patients with suspected pulmonary embolism, though less extensively studied, deserves attention. Benefits of echo/Doppler in these patients are as follows: (1) Echo/Doppler is a noninvasive, relatively inexpensive technique, readily available and repeatable in critically ill patients at the bedside. (2) Echo/Doppler provides a number of independent parameters related to the pulmonary hemodynamics. These parameters include: (a) characteristics of blood flow velocity curves across the right heart valves as well as systolic and diastolic time intervals of the right ventricle (b) motion pattern of the interventricular septum (c) dimensions of the heart chambers and inferior vena cava (d) thickness of the right ventricular free wall (3) Echocardiography allows detection of thrombi within right heart chambers or in major branches of the pulmonary artery in some patients. (4) Echo/Doppler may disclose alternative abnormalities explaining symptoms found in a patient with suspected pulmonary embolism such as pericardial disease, myocardial infarction, aortic dissection, hypovolemic shock, etc.