Bisulfite-containing propofol: is it a cost-effective alternative to Diprivan for induction of anesthesia?

Propofol (Diprivan(TM); AstraZeneca, Wilmington, DE) is a commonly used drug for the induction of general anesthesia in the ambulatory setting. With the availability of a new bisulfite-containing generic formulation of propofol, questions have arisen regarding its cost effectiveness and safety compared with Diprivan(TM). Two hundred healthy outpatients were randomly assigned, according to a double-blinded protocol, to receive either Diprivan(TM) or bisulfite-containing propofol 1.5 mg/kg IV as part of a standardized induction sequence. Maintenance of anesthesia consisted of either desflurane (4%-8% end-tidal) or sevoflurane (1%-2% end-tidal) in combination with a remifentanil infusion (0.125 microg x kg(-1) x min(-1) IV). Patient assessments included pain on injection, induction time, hemodynamic and bispectral electroencephalographic changes during induction, emergence time, and incidence of postoperative nausea and vomiting. The two propofol groups were comparable demographically, and the induction times and bispectral index values during the induction were also similar. However, the bisulfite-containing formulation was associated with less severe pain on injection (5% vs 11%), with fewer patients recalling pain on injection after surgery (38% vs. 51%, P<0.05). None of the patients manifested allergic-type reactions after the induction of anesthesia. The acquisition cost (average wholesale price in US dollars) of a 20-mL ampoule of Diprivan(TM) was $15 compared with $13 for the bisulfite-containing propofol formulation. Therefore, we concluded that the bisulfite-containing formulation of propofol is a cost-effective alternative to Diprivan(TM) for the induction of outpatient anesthesia.

IMPLICATIONS

Bisulfite-containing propofol and Diprivan(TM) (AstraZeneca, Wilmington, DE) were similar with respect to their induction characteristics; however, the generic formulation was associated with a smaller incidence of injection pain. Assuming that the drug costs are similar, these data suggest that the bisulfite-containing formulation of propofol is a cost-effective alternative to Diprivan(TM).

Solid-supported synthesis of a peptide beta-turn mimetic

[structure: see text]The solid-supported synthesis of a bicyclic diketopiperazine, a potential peptide beta-turn mimetic, is described. The Ugi reaction between the resin ester of alpha-N-Boc-diaminopropionic acid (an amine input), alpha-bromo acid, aldehyde, and isocyanide is the key step in the proposed protocol.

A novel testis-specific gene, SPAG4, whose product interacts specifically with outer dense fiber protein ODF27, maps to human chromosome 20q11.2

The product of the spermatid-specific rat SPAG4 gene interacts specifically with the major 27-kDa outer dense fiber protein ODF27 in elongating spermatids. In this study we isolated the human homolog of the spermatid-specific rat SPAG4 gene and mapped it by fluorescence in situ hybridization to chromosome 20q11.2.

Human outer dense fiber gene, ODF2, localizes to chromosome 9q34

We have isolated the human homolog of the rat Odf2 gene. In rat, Odf2, the 84-kDa major outer dense fiber protein, interacts strongly and specifically with Odf1, the 27-kDa major outer dense fiber protein. The interaction is mediated by leucine zippers during ODF assembly along the sperm axoneme. We compared homology and genomic structure to rat and mouse Odf2 genes. Using fluorescence in situ hybridization, we mapped the human Odf2 gene (ODF2) to chromosome 9q34.

Measuring the VC-dimension using optimized experimental design

VC-dimension is the measure of model complexity (capacity) used in VC-theory. The knowledge of the VC-dimension of an estimator is necessary for rigorous complexity control using analytic VC generalization bounds. Unfortunately, it is not possible to obtain the analytic estimates of the VC-dimension in most cases. Hence, a recent proposal is to measure the VC-dimension of an estimator experimentally by fitting the theoretical formula to a set of experimental measurements of the frequency of errors on artificially generated data sets of varying sizes (Vapnik, Levin, & Le Cun, 1994). However, it may be difficult to obtain an accurate estimate of the VC-dimension due to the variability of random samples in the experimental procedure proposed by Vapnik et al. (1994). We address this problem by proposing an improved design procedure for specifying the measurement points (i.e., the sample size and the number of repeated experiments at a given sample size). Our approach leads to a nonuniform design structure as opposed to the uniform design structure used in the original article (Vapnik et al., 1994). Our simulation results show that the proposed optimized design structure leads to a more accurate estimation of the VC-dimension using the experimental procedure. The results also show that a more accurate estimation of VC-dimension leads to improved complexity control using analytic VC-generalization bounds and, hence, better prediction accuracy.

Common fold in helix-hairpin-helix proteins

Helix-hairpin-helix (HhH) is a widespread motif involved in non-sequence-specific DNA binding. The majority of HhH motifs function as DNA-binding modules, however, some of them are used to mediate protein-protein interactions or have acquired enzymatic activity by incorporating catalytic residues (DNA glycosylases). From sequence and structural analysis of HhH-containing proteins we conclude that most HhH motifs are integrated as a part of a five-helical domain, termed (HhH)(2) domain here. It typically consists of two consecutive HhH motifs that are linked by a connector helix and displays pseudo-2-fold symmetry. (HhH)(2) domains show clear structural integrity and a conserved hydrophobic core composed of seven residues, one residue from each alpha-helix and each hairpin, and deserves recognition as a distinct protein fold. In addition to known HhH in the structures of RuvA, RadA, MutY and DNA-polymerases, we have detected new HhH motifs in sterile alpha motif and barrier-to-autointegration factor domains, the alpha-subunit of Escherichia coli RNA-polymerase, DNA-helicase PcrA and DNA glycosylases. Statistically significant sequence similarity of HhH motifs and pronounced structural conservation argue for homology between (HhH)(2) domains in different protein families. Our analysis helps to clarify how non-symmetric protein motifs bind to the double helix of DNA through the formation of a pseudo-2-fold symmetric (HhH)(2) functional unit.

A novel method to calculate the approximate derivative photoacoustic spectrum using continuous wavelet transform

A novel method based on continuous wavelet transform (CWT) using Haar wavelet function for approximate derivative calculation of analytical signals is proposed and successfully used in processing the photoacoustic signal. An approximate nth derivative of an analytical signal can be obtained by applying n times of the wavelet transform to the signal. The results obtained from four other different methods--the conventional numerical differentiation, the Fourier transform method, the Savitzky-Golay method, and the discrete wavelet transform (DWT) method--were compared with the proposed CWT method; it was demonstrated that all the results are almost the same for signals without noise, but the proposed CWT method is superior to the former four methods for noisy signals. The approximate first and second derivative of the photoacoustic spectrum of Pr(Gly)3Cl3.3H2O and PrCl3.6H2O were obtained using the proposed CWT method; the results are satisfactory.

[Value of condensation and rarefaction click evoked action potential latency difference in the diagnosis of Meniere's disease]

OBJECTIVE

To study the value of condensation and rarefaction clicks evoked action potential (AP) latency difference (LD) in diagnosis of Meniere's disease.

METHODS

AP was recorded with ECochG in controls (50 ears) and patients with Meniere's disease(90 ears) and sensorineural hearing loss(SNHL) of other origins(60 ears). LD was calculated and analyzed.

RESULTS

LD in patients with Meniere's disease was (0.30 +/- 0.15) ms, which was significantly larger than that of controls(0.18 +/- 0.07) ms and of patients with SNHL of other origins(0.20 +/- 0.10) ms (P < 0.01). In the group of Meniere's disease, LD in patients with the mild and moderate hearing impairment was larger than those with severe hearing loss(P < 0.01) and LD in patients with low tone or high tone auditory sensation curve was larger than those with flat auditory sensation curve(P < 0.01). Positive rate was 4/60(6.7%) in other SNHL patients and 58/90(64.0%) in Meniere's disease group respectively.

CONCLUSION

The increase in condensation and rarefaction click evoked AP latency difference can be an objective parameter in diagnosis of Meniere's disease.

Roles of the histone H2A-H2B dimers and the (H3-H4)(2) tetramer in nucleosome remodeling by the SWI-SNF complex

SWI-SNF is an ATP-dependent chromatin remodeling complex required for expression of a number of yeast genes. Previous studies have suggested that SWI-SNF action may remove or rearrange the histone H2A-H2B dimers or induce a novel alteration in the histone octamer. Here, we have directly tested these and other models by quantifying the remodeling activity of SWI-SNF on arrays of (H3-H4)(2) tetramers, on nucleosomal arrays reconstituted with disulfide-linked histone H3, and on arrays reconstituted with histone H3 derivatives site-specifically modified at residue 110 with the fluorescent probe acetylethylenediamine-(1,5)-naphthol sulfonate. We find that SWI-SNF can remodel (H3-H4)(2) tetramers, although tetramers are poor substrates for SWI-SNF remodeling compared with nucleosomal arrays. SWI-SNF can also remodel nucleosomal arrays that harbor disulfide-linked (H3-H4)(2) tetramers, indicating that SWI-SNF action does not involve an obligatory disruption of the tetramer. Finally, we find that although the fluorescence emission intensity of acetylethylenediamine-(1,5)-naphthol sulfonate-modified histone H3 is sensitive to octamer structure, SWI-SNF action does not alter fluorescence emission intensity. These data suggest that perturbation of the histone octamer is not a requirement or a consequence of ATP-dependent nucleosome remodeling by SWI-SNF.

Reversed-phase liquid chromatography of proteins and peptides using multimodal copolymer-encapsulated silica

Multimodal copolymer-encapsulated particles for liquid chromatography were prepared by bonding 1-octadecene and unsaturated carboxylic acids on silica particles (5 microm diameter, 300 A pores) for liquid chromatography of proteins. These multimodal copolymer-encapsulated particles can provide both hydrophobic and hydrogen bonding interactions with polar compounds. The chromatographic performance of these multimodal copolymer-encapsulated particles for peptide and protein separations was evaluated under reversed-phase conditions. Compared with typical C8-bonded silica, polymer-encapsulated particles were more stable in acidic mobile phases and provided better recoveries, especially for large proteins (Mr>0.5 x 10(6)). Totally hydrophobic polymer-encapsulated particles were found to produce broad peaks for proteins, and significant improvements were observed by introducing hydrophilic groups (-COOH) onto the polymer-encapsulated surface to form a multimodal phase. For the reversed-phase liquid chromatography of peptides and proteins, improved selectivity and increased solute retention were found using the multimodal polymer-encapsulated particles. More peaks were resolved for the separation of complex peptide mixtures such as protein digests using the multimodal polymer-encapsulated particles as compared to totally hydrophobic polymer-encapsulated particles.

An immune algorithm for resolution of multicomponent overlapping chromatograms

A novel immune algorithm for resolution and quantitative determination of the components in overlapping chromatograms was proposed by imitating biological immune systems. The algorithm takes an overlapping chromatogram as its input and subtracts the chromatograms of standard samples from the input by iteration of a network. When the residual does not change, the network will converge and chromatographic information of the components in overlapping chromatogram will be obtained. Both simulated and experimental data sets were investigated by the method. Results showed that both resolved results and recoveries of quantitative determination are satisfactory. Comparing with conventional least-square method, the immune algorithm is fast in calculation.

Identification of a 5-cM region of common allelic loss on 8p12-p21 in human breast cancer and genomic analysis of the hEXT1L/EXTR1/EXTL3 gene in this locus

The short arm of chromosome 8 is frequently lost in many human carcinomas including breast cancer, suggesting the presence of a tumor suppressor gene(s) in this region. We identified a gene termed hEXT1L/EXTR1/EXTL3 (hEXT1L hereinafter) that was mapped to chromosome bands 8p12-p21 where frequent LOHs of this region was reported in breast cancer. The existence of the third breast cancer susceptibility gene was also suggested in this region by linkage analysis. We further performed LOH analysis in 8p12-p21 in 34 breast cancers and identified a 5-cM region of common allelic loss that overlapped with the locus for positive lod score in familial breast cancer. We further analyzed genomic alterations of hEXT1L in tumors in which frequent LOHs of 8p were reported. A total of 327 cancers (313 primary tumors and 14 cancer cell lines) including 22 primary breast cancers were analyzed, but none of the tumors had somatic mutations: only one thyroid cancer patient without any family history of cancer had a 9-bp insertion in the constitutional DNA. These results suggest that mutations of hEXT1L do not play a major role in the development of sporadic cancers including breast cancer, and that other tumor suppressor gene(s) exists in the 5-cM region identified in this study.

Spag4, a novel sperm protein, binds outer dense-fiber protein Odf1 and localizes to microtubules of manchette and axoneme

Outer dense fibers are structures unique to the sperm tail. No definite function for these fibers has been found, but they may play a role in motility and provide elastic recoil. Their composition had been described before, but only two of the fiber proteins, Odf1 and Odf2, are cloned. We cloned Odf2 by virtue of its functional and specific interaction with Odf1, which, we show, is mediated by a leucine zipper. Further work demonstrated that the 84-kDa Odf2 protein localizes to both the cortex and the medulla of the fibers, whereas the 27-kDa Odf1 protein is present only in the medulla. Here we report the cloning and characterization of a new Odf1-interacting protein, Spag4. Spag4 mRNA is spermatid specific, and the 49-kDa Spag4 protein complexes specifically with Odf1, but not Odf2, mediated by a leucine zipper. It also self-associates. In contrast to Odf1 and Odf2, Spag4 protein localizes to two microtubule-containing spermatid structures. Spag4 is detectable in the transient manchette and it is associated with the axoneme in elongating spermatids and epididymal sperm. Our data suggest a role for Spag4 in protein localization to two major sperm tail structures.

[The treatment of 432 patients with pituitary adenomas via transsphenoidal approach]

OBJECTIVE

To study some clinical features of 432 cases of pituitary adenomas treated by transsphenoidal microsurgery between July 1982 and October 1996.

METHODS

Pathological examination, immunohistochemical examination and electronmicroscopic examination were done in 424, 29 and 103 cases respectively.

RESULTS

Hyperprolactinemia was found in many so-called non-functioning adenomas besides in prolactinomas. The dura maters were invaded by tumors in 78 cases (the incidence of dural invasion was 65.5%).

CONCLUSIONS

Hyperprolactinemia is not peculiar to prolactinomas, and differential diagnosis is necessary when hyperprolactinemia exists. The involvement of the dura mater of sellar floor is an important mark that the adjacent tissues were invaded by pituitary adenomas. The outcome of surgical treatment is significantly different between the patients with dural invasion and without invasion.

[Studies on data compression of 1-D NMR spectra using wavelet transform]

The multiresolution signal decomposition (MRSD) algorithm based on wavelet transform was applied to the compression of 1-D NMR spectra. A NMR spectrum which was composed of 32768 data points was investigated and the spectrum can be completely reconstructed with the residual square deviation (RSD) being as small as 2.7769 x 10(-4) when the spectrum was compressed to 512 data points. The relationship among the RSD and the different wavelet function, number of decomposiion and the compression ratio was also discussed.

Capillary electrophoresis using diol-bonded fused-silica capillaries

In this paper, 3-glycidoxypropyltrimethoxysilane was used to produce diol-bonded capillaries at room temperature for capillary electrophoresis (CE). A variety of standard reference compounds and authentic biological samples including ribonucleotides, peptides and proteins were used to test the columns. It was found that greatly suppressed electroosmotic flow was measured over a pH range of 3-10. Lower than 1.6% relative standard deviation (> 10 runs) in migration time was observed for the analysis of test proteins. For real samples of ribonucleotides in tumor cell extracts, approximately 1 million theoretical plates and excellent peak shapes were obtained. The high column efficiency and symmetrical peaks allowed the separation of samples with only 0.6% maximum difference in migration times. The diol-bonded fused-silica capillary columns were stable when used in a pH range of 2-8 under typical CE conditions. The column preparation method involved a simple dynamic coating procedure at room temperature, greatly simplifying the more typical static coating methods that require vacuum pumps and ovens.

Solution structures of the Ca2+-free and Ca2+-bound C2A domain of synaptotagmin I: does Ca2+ induce a conformational change?

C2 domains are widespread Ca2+-binding modules that are particularly abundant in proteins involved in membrane traffic and signal transduction. The C2A domain of synaptotagmin I is believed to play a key role in neurotransmitter release through its Ca2+-dependent interactions with syntaxin and phospholipids. Elucidating the structural consequences of Ca2+ binding to the C2A domain is critical for understanding its mechanism of action and for models of the functions of other C2 domains. We have determined the solution structure of the Ca2+-free and Ca2+-bound forms of the C2A domain of synaptotagmin I by NMR spectroscopy. Our data represent the first structure determination of a C2 domain in its Ca2+-free and Ca2+-bound forms. Three Ca2+ ions were included in the Ca2+-bound structure, yielding a Ca2+-binding motif that involves five aspartate side chains and one serine side chain. Ca2+ immobilizes the structure of the C2A domain but does not produce a significant conformational change from a well-defined conformation to another. Thus, the mechanism of action of the C2A domain of synaptotagmin I is different from that used by Ca2+-binding proteins of the EF-hand family. The main effect of Ca2+ binding on the C2A domain is to change its electrostatic potential rather than its structure. These results support a model whereby the C2A domain functions as an electrostatic switch in neurotransmitter release. The similarity between the structures of the synaptotagmin I C2A domain and the PLC-delta1 C2 domain suggests that the latter binds four Ca2+ ions and acts by a similar mechanism. This mechanism may also be valid for other C2 domains that share the unusual ability to bind multiple Ca2+ ions in a tight cluster at the tip of the domain.

[Separation and determination of eight plant hormones by reversed-phase high performance liquid chromatography]

In this paper, reversed-phase high performance liquid chromatographic technique was used for the separation and determination of eight plant hormones. Methanol-water-acetic acid system was chosen as the mobile phase. The effects of different separation conditions, such as the methanol and acetic acid concentrations in mobile phase, on the retention behaviours of eight plant hormones in this system were studied. The general trends in retention behaviours could be correlated to the methanol concentration in mobile phase. The experimental results showed that the optimum separation was achieved with following gradient elution condition: 0-3 minutes, 70% (water percentage in mobile phase), 3-13 minutes, 70%-20%, 13-48 minutes, 20%. Benzene was added to be as the internal standard. Under this experimental condition, the eight plant hormones could be separated completely and detected quantitatively at 260 nm within 16 minutes. The calibration curves for the eight compounds gave linearity over a wide range. The correlation coefficients of each components were r(ZT) = 0.9971, r(GAs) = 0.9999, r(K) = 0.9997, r(BA) = 0.9995, r(IAA) = 0.9998, r(IPA) = 0.9982, r(IBA) = 0.9995 and r(NAA) = 0.9995. The method is rapid, simple and efficient. It is a suitable method for the accurate determination of gibberellic acid (GA) and alpha-naphthaleneacetic acid (alpha-NAA) in products for agricultural use.

Mutational analysis of the PTEN gene in head and neck squamous cell carcinoma

Loss of heterozygosity (LOH) at chromosome band 10q23 occurs frequently in a wide variety of human tumors. A recently identified candidate tumor suppressor gene, PTEN located on 10q23, is mutated in multiple advanced cancers. To explore whether PTEN is associated with human squamous cell carcinoma of the head and neck (SCCHN), DNAs from both normal muscle and tumor tissue in 19 SCCHN were used for detecting LOH at chromosome 10q23 and mutational analysis of PTEN by direct polymerase chain reaction (PCR)-DNA sequencing. LOH at 10q23 was identified in 6/15 SCCHN. Mutation of PTEN was identified in 3/19 SCCHN. Of these 3 patients, 2 had stage IV disease; the third patient, with recurrent, metastatic and stage III disease, showed a 36 bp germline heterozygous deletion within intron 7. Furthermore, a missense mutation at codon 501 (TCT --> TTT: Ser --> Phe) in exon 8 was also found in tumor from the same patient. Our results suggest that PTEN may play a role in the genesis of some SCCHNs.

Mutational analysis of the PTEN gene in head and neck squamous cell carcinoma

Loss of heterozygosity (LOH) at chromosome band 10q23 occurs frequently in a wide variety of human tumors. A recently identified candidate tumor suppressor gene, PTEN located on 10q23, is mutated in multiple advanced cancers. To explore whether PTEN is associated with human squamous cell carcinoma of the head and neck (SCCHN), DNAs from both normal muscle and tumor tissue in 19 SCCHN were used for detecting LOH at chromosome 10q23 and mutational analysis of PTEN by direct polymerase chain reaction (PCR)-DNA sequencing. LOH at 10q23 was identified in 6/15 SCCHN. Mutation of PTEN was identified in 3/19 SCCHN. Of these 3 patients, 2 had stage IV disease; the third patient, with recurrent, metastatic and stage III disease, showed a 36 bp germline heterozygous deletion within intron 7. Furthermore, a missense mutation at codon 501 (TCT --> TTT: Ser --> Phe) in exon 8 was also found in tumor from the same patient. Our results suggest that PTEN may play a role in the genesis of some SCCHNs.

Developmental expression of the 84-kDa ODF sperm protein: localization to both the cortex and medulla of outer dense fibers and to the connecting piece

Outer dense fibers (ODF) are specialized cytoskeletal elements of the mammalian sperm tail which are composed of several prominent proteins. We previously reported the isolation of a cDNA (111-450) encoding a putative 84-kDa ODF protein. Here we demonstrate by independent cDNA isolations and by translational/immunoprecipitation of testicular mRNAs using anti-ODF 84 antibodies that 111-450 cDNA encodes the 84-kDa protein. We then analyzed the testicular expression of the ODF 84 mRNA and protein. Riboprobes generated from the clones recognized four testicular-specific transcripts of 1.6, 2.2, 2.4, and 2.8 kb in both rat and bull of which the immunoprecipitable product of the 2.4-kb mRNA comigrates with ODF 84 protein. Developmental Northerns indicated that the 2.2- and 2.4-kb mRNAs are first transcribed during meiotic prophase while the other two species are first expressed in round spermatids. The levels of all the transcripts steadily increased up to elongated spermatids. Immunocytochemistry revealed that the anti-84 reactive ODF proteins were synthesized and assembled in the cytoplasm of elongated spermatids (steps 9-18) with peak activity occurring in step 16 of spermiogenesis. Immunogold labeling was selective to the assembling ODF and connecting piece of the tail and to granulated bodies of the cytoplasmic lobe. Both the striated collar and capitulum of the connecting piece were immunolabeled as well as the basal plate of the implantation fossa. A combination of pre- and postembedding immunogold labeling provided evidence that the 84-kDa ODF protein is localized to both the cortex and medulla of the ODF in contrast to the sole medullary localization of the major 27-kDa ODF protein. Thus the 84-kDa ODF protein, encoded by the 2.4 transcript, is translationally regulated, packaged after synthesis into granulated bodies, assembled in a proximal to distal direction along the axoneme and may interact by means of leucine zippers specifically with the 27-kDa ODF protein during assembly. Its localization to both the cortex and medulla of the ODF, as opposed to exclusive medullary localization of the 27-kDa ODF protein, and the presence of two leucine zippers, only one of which interacts with the 27-kDa ODF, suggests that it could act as a link between proteins of the two regions of the ODF.

Ca2+ binding to synaptotagmin: how many Ca2+ ions bind to the tip of a C2-domain?

C2-domains are widespread protein modules with diverse Ca2+-regulatory functions. Although multiple Ca2+ ions are known to bind at the tip of several C2-domains, the exact number of Ca2+-binding sites and their functional relevance are unknown. The first C2-domain of synaptotagmin I is believed to play a key role in neurotransmitter release via its Ca2+-dependent interactions with syntaxin and phospholipids. We have studied the Ca2+-binding mode of this C2-domain as a prototypical C2-domain using NMR spectroscopy and site-directed mutagenesis. The C2-domain is an elliptical module composed of a beta-sandwich with a long axis of 50 A. Our results reveal that the C2-domain binds three Ca2+ ions in a tight cluster spanning only 6 A at the tip of the module. The Ca2+-binding region is formed by two loops whose conformation is stabilized by Ca2+ binding. Binding involves one serine and five aspartate residues that are conserved in numerous C2-domains. All three Ca2+ ions are required for the interactions of the C2-domain with syntaxin and phospholipids. These results support an electrostatic switch model for C2-domain function whereby the beta-sheets of the domain provide a fixed scaffold for the Ca2+-binding loops, and whereby interactions with target molecules are triggered by a Ca2+-induced switch in electrostatic potential.

Single-tryptophan mutants of monomeric tryptophan repressor: optical spectroscopy reveals nonnative structure in a model for an early folding intermediate

A monomeric version of the dimeric tryptophan repressor from Escherichia coli, L39E TR, has previously been shown to resemble a transient intermediate that appears in the first few milliseconds of folding [Shao, X., Hensley, P., and Matthews, C. R. (1997) Biochemistry 36, 9941-9949]. In the present study, the optical properties of the two intrinsic tryptophans were used to compare the structure and dynamics of the monomeric form with those of the native, dimeric form. The urea-induced unfolding equilibria of Trp19/L39E TR (Trp99 replaced with Phe) and Trp99/L39E TR (Trp19 replaced with Phe) mutants were monitored by circular dichroism and fluorescence spectroscopies at pH 7.6 and 25 degrees C. Coincident normalized transitions show that the urea denaturation process for each single-tryptophan mutant follows a two-state model involving monomeric native and unfolded forms. The free energies at standard state in the absence of denaturant for Trp19/L39E TR and Trp99/L39E TR are less than that for L39E TR, indicating that both tryptophans are involved in stabilizing the monomer. Fluorescence and near-UV circular dichroism spectroscopies indicate that the tryptophan side chains in monomeric Trp19/L39E TR and Trp99/L39E TR occupy hydrophobic, well-structured environments that are distinctively different from those found in their dimeric counterparts. Acrylamide quenching experiments show that both Trp19 and Trp99 are partially exposed to solvent in the native state, with Trp99 having a slightly greater degree of exposure. Measurements of the steady-state anisotropies of Trp19/L39E and Trp99/L39E TR demonstrate that the motions of both tryptophan side chains are restricted in the folded conformation. On the basis of these data, it can be concluded that this monomeric form of the tryptophan repressor adopts a well-folded, stable conformation with nonnative tertiary structure. When combined with previous results, the current findings demonstrate that the development of higher order structure during the folding of this intertwined dimer does not follow a simple hierarchical model.