Bioanalytical applications of surface-enhanced Raman spectroscopy: de novo molecular identification

Surface enhanced Raman scattering (SERS) has become a powerful technique for trace analysis of biomolecules. The use of SERS-tags has evolved into clinical diagnostics, the enhancement of the intrinsic signal of biomolecules on SERS active materials shows tremendous promise for the analysis of biomolecules and potential biomedical assays. The detection of the de novo signal from a wide range of biomolecules has been reported to date. In this review, we examine different classes of biomolecules for the signals observed and experimental details that enable their detection. In particular, we survey nucleic acids, amino acids, peptides, proteins, metabolites, and pathogens. The signals observed show that the interaction of the biomolecule with the enhancing nanostructure has a significant influence on the observed spectrum. Additional experiments demonstrate that internal standards can correct for intensity fluctuations and provide quantitative analysis. Experimental methods that control the interaction at the surface are providing for reproducible SERS signals. Results suggest that combining advances in methodology with the development of libraries for SERS spectra may enable the characterization of biomolecules complementary to other existing methods.

Effect of apocynin on ozone-induced airway hyperresponsiveness to methacholine in asthmatics

Apocynin is an inhibitor of NADPH oxidase present in inflammatory cells such as eosinophils and neutrophils. We investigated the effect of inhaled apocynin on ozone-induced bronchial hyperresponsiveness in vivo. Seven mild atopic asthmatics participated in a placebo-controlled, cross-over study with two exposures to O(3) at 2-week intervals. Apocynin (3 ml of 0.5 mg/ml) was inhaled 2 times before and 6 times after O(3) exposure at hourly intervals. At 36 h before and 16 h after O(3) exposure, methacholine inhalation challenge tests (Mch) were performed, and PC(20) and maximal % fall from baseline (MFEV(1)) were calculated from dose-response curves. O(3)-induced change in PC(20) (Delta PC(20)) after placebo treatment was -1.94 +/- 0.39 DD (mean +/- SEM doubling dose Mch) (p =.001) and apocynin was -0.6 +/- 0.33 DD (p =.17). The difference between apocynin and placebo treatment was 1.3 DD +/- 0.42 (p =.02). O(3)-induced Delta MFEV(1) was 11.9 +/- 1.5% (p =.008) during placebo inhalation and 3.85 +/- 1.8% during apocynin (p =.47). Apocynin reduced the Delta MFEV(1) by 8.05% compared to placebo (p =.025). We conclude that apocynin markedly reduced O(3)-induced hyperreactivity for Mch as well as maximal airway narrowing. The results suggest that apocynin may have a role in preventing ozone-induced exacerbations of asthma.

Caging of a d-dimensional sphere and its relevance for the random dense sphere packing

We analyze the caging of a hard sphere (i.e., the complete arrest of all translational motions) by randomly distributed static contact points on the sphere surface for arbitrary dimension d>/=1, and prove that the average number of uncorrelated contacts required to cage a sphere is <N>(d)=2d+1. Computer simulations, which confirm this analytical result, are also used to model the effect of correlations between contacts that occur in real hard-sphere systems. Our analysis predicts an average coordination number of 4.79 (+/-0.02) for caged spheres, which agrees surprisingly well with the experimental coordination number for random sphere packings reported by Mason [Nature 217, 733 (1968)]. This result supports the physical picture that the coordination number in random dense sphere packings is primarily determined by caging effects. It also suggests that it should be possible to construct such packings from a local caging rule.

Ozone-induced airway hyperresponsiveness in patients with asthma: role of neutrophil-derived serine proteinases

Proteinase inhibitors may be of potential therapeutic value in the treatment of respiratory diseases such as chronic obstructive pulmonary disease (COPD) or asthma. Our aim was to study the role of neutrophils, and neutrophil-derived serine proteinases in an acute model in patients with asthma. Exposure to ozone induces an acute neutrophilic inflammatory reaction accompanied by an increase in airway hyperresponsiveness. It is thought that these two effects of ozone are linked, and that neutrophil-derived serine proteinases (i.e. elastase) may play a role in the ozone-induced airway hyperresponsiveness. Therefore, we examined the effect of recombinant antileukoprotease (rALP), one of the major serine proteinase inhibitors in the lung, on ozone-induced changes in airway hyperresponsiveness in this model. We observed that 16 h after exposure to ozone, airway hyperresponsiveness to methacholine was increased both following placebo and rALP treatment. There was no significant difference between placebo and rALP treatment (change in area under the dose-response curve to methacholine: 117.3+/-59.0 vs 193.6+/-59.6 % fall x DD; p=.12). Moreover, the immediate decrease in FEV1 after ozone exposure was not significantly different between the two groups (placebo: -29.6+/-6.7%; rALP: -20.9+/-3.8%; p=.11). In addition, no significant differences were observed in plasma levels of fibrinogen degradation products generated by neutrophil serine proteinases before and after exposure to ozone. We conclude that neutrophil-derived serine proteinases are not important mediators for ozone-induced hyperresponsiveness.

Membrane insertion defects caused by positive charges in the early mature region of protein pIII of filamentous phage fd can be corrected by prlA suppressors

The filamentous phage coat protein pIII has been used to display a variety of peptides and proteins to allow easy screening for desirable binding properties. We have examined the biological constraints that restrict the expression of short peptides located in the early mature region of pIII, adjacent to the signal sequence cleavage site. Many functionally defective pIII fusion proteins contained several positively charged amino acids in this region. These residues appear to inhibit proper insertion of pIII into the Escherichia coli inner membrane, blocking the assembly and extrusion of phage particles. Suppressor mutations in the prlA (secY) component of the protein export apparatus dramatically alleviate the phage growth defect caused by the positively charged residues. We conclude that insertion of pIII fusion proteins into the inner membrane can occur by a sec gene-dependent mechanism. The suppressor strains should be useful for increasing the diversity of peptides displayed on pIII in phage libraries.

Mortality prediction and interval until death in near-term and term neonates with respiratory failure

Mortality risk indicators may be useful adjuncts to clinical judgment in considering the use of extraordinary and relatively high-risk treatments such as high-frequency ventilation, extracorporeal membrane oxygenation, and nitric oxide therapy. We retrospectively evaluated the reliability of published indications of high mortality, developed additional high-risk indicators, and determined the interval between the time when high-risk indicators were met and when death occurred in near-term and term neonates with respiratory failure. Patients were included in the analysis if they met the following criteria: > or = 35 weeks gestation, > or = 2 kg birth weight, < or = 7 days of age, and receiving a fraction of inspired oxygen of > or = 0.8 and mechanical ventilation. Patients were excluded if they had congenital heart disease, intracranial hemorrhage, untreatable bleeding diathesis, or lethal congenital anomaly. Fifteen patients in the 1980 to 1981 group and 41 patients in the 1985 to 1987 group met these criteria. We observed 100% mortality in our 1980 to 1981 patients who met previously published criteria predictive for > or = 80% mortality in near-term and term neonates with respiratory failure; however, mortality risk was 60% to 80% in the 1985 to 1987 group.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective enrichment and characterization of high affinity ligands from collections of random peptides on filamentous phage

Large collections of random peptides can be expressed on the N-terminus of the pIII protein of filamentous phage and screened for binding to antibodies and other receptors. In our previous work with a monoclonal antibody (3E7) (Cwirla et al., Proc. Natl. Acad. Sci. USA 87, 6378-6382, 1990), we showed that a high proportion of the selected peptides had relatively low affinity (Kd's greater than 1 microM). Here we describe conditions for selective enrichment of phage expressing high affinity peptides. This is done by allowing the phage to interact with a low concentration of 3E7 Fab followed by extensive washing to allow dissociation of phage-bearing peptides with low affinity. These affinity selection conditions were applied to the pool of phage previously selected using a high concentration of IgG. A phage clone with the known high affinity ligand YGGFL (Kd 7.1 nM) and several other closely related peptides were isolated. The dissociation rate of 125I-3E7 Fab from several phage clones approximated that of phage expressing YGGFL. A good correlation was found between the dissociation rate of the peptides found on phage and the equilibrium binding constants of chemically synthesized peptides. The strategy of using a low concentration of receptor and extensive washing to select phage-bearing high affinity peptides, combined with assays to determine the specificity and relative affinity of peptides on isolated phage clones, should be generally applicable in using the peptides-on-phage system for discovery of high affinity receptor ligands.

Pulmonary hypoplasia and persistent pulmonary hypertension: favorable clinical response to high-frequency jet ventilation

Pulmonary hypoplasia in the neonate is frequently fatal. This article reports two neonates with a clinical diagnosis of pulmonary hypoplasia complicated by persistent pulmonary hypertension (PPHN). Though both infants were progressively worsening while receiving conventional mechanical ventilatory support, they survived when treated with high-frequency jet ventilation.

Peptides on phage: a vast library of peptides for identifying ligands

We have constructed a vast library of peptides for finding compounds that bind to antibodies and other receptors. Millions of different hexapeptides were expressed at the N terminus of the adsorption protein (pIII) of fd phage. The vector fAFF1, derived from the tetracycline resistance-transducing vector fd-tet, allows cloning of oligonucleotides in a variety of locations in the 5' region of gene III. A library of 3 x 10(8) recombinants was generated by cloning randomly synthesized oligonucleotides. The library was screened for high-avidity binding to a monoclonal antibody (3-E7) that is specific for the N terminus of beta-endorphin (Tyr-Gly-Gly-Phe). Fifty-one clones selected by three rounds of the affinity purification technique called panning were sequenced and found to differ from previously known ligands for this antibody. The striking finding is that all 51 contained tyrosine as the N-terminal residue and that 48 contained glycine as the second residue. The binding affinities of six chemically synthesized hexapeptides from this set range from 0.35 microM (Tyr-Gly-Phe-Trp-Gly-Met) to 8.3 microM (Tyr-Ala-Gly-Phe-Ala-Gln), compared with 7.1 nM for a known high-affinity ligand (Tyr-Gly-Gly-Phe-Leu). These results show that ligands can be identified with no prior information concerning antibody specificity. Peptide libraries are also likely to be useful in finding ligands that bind to other classes of receptors and in discovering pharmacologic agents.

Inverse relationship between proliferation and differentiation in a human TNP-specific B cell line. Cell cycle dependence of antibody secretion

Studies of an EBV-transformed and TNP-specific human B cell line revealed that, unlike myeloma or hybridoma cell lines that consist mainly of fully differentiated cells, most of the cloned EBV-transformed cells were not fully differentiated, as judged by inability to bind TNP-SRBC and to secrete anti-TNP antibody. The minority of more differentiated cells were selected by TNP-SRBC rosetting. They were found to proliferate to a lesser extent than nonrosetting cells and to contain increased numbers of antibody-secreting cells. This inverse relationship between proliferation and differentiation was also shown to be cell cycle related in that the TNP-SRBC rosetting cells resided, to a greater extent than the nonrosetting cells, in the G1 phase of the cell cycle. The finding that the G1 phase of the cell cycle was associated with differentiation into anti-TNP secreting cells was confirmed by demonstrating that treatment with hydroxyurea, which arrests the cells in G1, resulted in decreased proliferation and an increased proportion of antibody-secreting cells. Similarly, addition of phorbol ester resulted in increased antibody secretion and decreased proliferation, suggesting a role for protein kinase C in this differentiation pathway. The strategy of increasing the number of antibody-producing cells in this human EBV line, by promoting differentiation of the cells in G1, may be relevant to the large scale production of specific human mAb for the treatment and diagnosis of human diseases.

Inverse relationship between proliferation and differentiation in a human TNP-specific B cell line. Cell cycle dependence of antibody secretion

Studies of an EBV-transformed and TNP-specific human B cell line revealed that, unlike myeloma or hybridoma cell lines that consist mainly of fully differentiated cells, most of the cloned EBV-transformed cells were not fully differentiated, as judged by inability to bind TNP-SRBC and to secrete anti-TNP antibody. The minority of more differentiated cells were selected by TNP-SRBC rosetting. They were found to proliferate to a lesser extent than nonrosetting cells and to contain increased numbers of antibody-secreting cells. This inverse relationship between proliferation and differentiation was also shown to be cell cycle related in that the TNP-SRBC rosetting cells resided, to a greater extent than the nonrosetting cells, in the G1 phase of the cell cycle. The finding that the G1 phase of the cell cycle was associated with differentiation into anti-TNP secreting cells was confirmed by demonstrating that treatment with hydroxyurea, which arrests the cells in G1, resulted in decreased proliferation and an increased proportion of antibody-secreting cells. Similarly, addition of phorbol ester resulted in increased antibody secretion and decreased proliferation, suggesting a role for protein kinase C in this differentiation pathway. The strategy of increasing the number of antibody-producing cells in this human EBV line, by promoting differentiation of the cells in G1, may be relevant to the large scale production of specific human mAb for the treatment and diagnosis of human diseases.

Morphology and behaviour of neural crest cells of chick embryo in vitro

Neural primordia of chick embryos were cultured for three days and the behaviour of migrating neural crest cells studied. Somite cells were used as a comparison. Crest cells were actively multipolar with narrow projections which extended and retracted rapidly, contrasting to the gradual extension of somite-cell lamelleae. On losing cell contact, somite cells were also more directionally persistent. The rate of displacement of isolated crest cells was particularly low when calculated over a long time base. Both crest and somite cells were monolayered; contact paralysis occurred in somite cell collisions but was not ascertained for crest cells. However, crest cells in a population were far more directionally persistent than isolated cells. Contact duration between crest cells increased with time and they formed an open network. Eventually, retraction clumping occurred, initially and chiefly at the periphery of the crest outgrowth. Crest cells did not invade cultured embryonic mesenchymal or epithelial populations but endoderm underlapped them. No effects were observed on crest cells prior to direct contact. Substrate previously occupied by endoderm of ectoderm caused crest cells to flatten while substrate previously occupied by the neural tube caused them to round up and clump prematurely.

Infections of the Eustachian Tube and Pulmonary Tract: (Section of Otology)

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Extensive Bony Growth of the Nasal Septum in a Woman 46 years of age

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