The linac coherent light source single particle imaging road map

Intense femtosecond x-ray pulses from free-electron laser sources allow the imaging of individual particles in a single shot. Early experiments at the Linac Coherent Light Source (LCLS) have led to rapid progress in the field and, so far, coherent diffractive images have been recorded from biological specimens, aerosols, and quantum systems with a few-tens-of-nanometers resolution. In March 2014, LCLS held a workshop to discuss the scientific and technical challenges for reaching the ultimate goal of atomic resolution with single-shot coherent diffractive imaging. This paper summarizes the workshop findings and presents the roadmap toward reaching atomic resolution, 3D imaging at free-electron laser sources.

High-intensity double-pulse X-ray free-electron laser

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.

Two-colour X-ray pulses from free-electron lasers can be used to probe ultrafast dynamics, but the total power is a fraction of the saturation power. Here, Marinelli et al. use twin electron bunches to reach full saturation power and increase the two-colour intensity by an order of magnitude at hard-X-ray energies.

Demonstration of single-crystal self-seeded two-color x-ray free-electron lasers

A scheme for generating two simultaneous hard-x-ray free-electron laser pulses with a controllable difference in photon energy is described and then demonstrated using the self-seeding setup at the Linac Coherent Light Source (LCLS). The scheme takes advantage of the existing LCLS equipment, which allows two independent rotations of the self-seeding diamond crystal. The two degrees of freedom are used to select two nearby crystal reflections, causing two wavelengths to be present in the forward transmitted seeding x-ray pulse. The free-electron laser system must support amplification at both desired wavelengths.

Beamline AR-NW12A: high-throughput beamline for macromolecular crystallography at the Photon Factory

AR-NW12A is an in-vacuum undulator beamline optimized for high-throughput macromolecular crystallography experiments as one of the five macromolecular crystallography (MX) beamlines at the Photon Factory. This report provides details of the beamline design, covering its optical specifications, hardware set-up, control software, and the latest developments for MX experiments. The experimental environment presents state-of-the-art instrumentation for high-throughput projects with a high-precision goniometer with an adaptable goniometer head, and a UV-light sample visualization system. Combined with an efficient automounting robot modified from the SSRL SAM system, a remote control system enables fully automated and remote-access X-ray diffraction experiments.

X-ray phase imaging of biological soft tissue using a direct-sensing x-ray HARP tube camera

A HDTV camera having a direct-sensing x-ray high-gain avalanche rushing amorphous photoconductor (HARP) tube was used, for the first time, to acquire x-ray phase maps. The tube can achieve a high sensitivity as a result of the avalanche multiplication process in the HARP target. A beryllium plate, rather than a glass plate, was used as the face plate of the tube to minimize the loss of x-rays due to absorption, and a 15 microm thick HARP target was directly formed on it. In the experiment, the x-ray phase shifts produced by a rat liver were measured using synchrotron x-rays (lambda = 0.0766 nm) and a triple Laue-case (LLL) x-ray interferometer. Interference patterns produced by the sample were observed with the direct-sensing x-ray HARP tube camera. A voltage of 1300 V was applied to the HARP target to give an output signal gain of two. The camera was operated in 1125 scanning-line mode, and real-time images were stored on a workstation at a rate of 30 images/s with an image format of 960 (H) x 1100 (V) pixels. A phase-map image of the sample was successfully obtained using the fringe scanning method and phase unwrapping. The observed phase shifts ranged from 50 degrees to 200 degrees . Trees of blood vessels in the rat liver were clearly depicted without using a contrast agent. The spatial resolution of the x-ray camera was estimated to be better than 35 microm in the vertical direction and 100 microm in the horizontal direction.

Molecular cloning, functional expression and characterization of p15, a novel fungal protein with potent neurite-inducing activity in PC12 cells

p15 is a novel fungal protein which induces neurite outgrowth and neuronal differentiation of PC12 cells. In the present study, we report molecular cloning, functional expression and characterization of the gene encoding p15. The deduced amino acid sequence suggested that p15 is synthesized as a precursor with 31 extra amino-terminal amino acids including a putative signal sequence, and 20 carboxy-terminal amino acids, in addition to the 118 amino acids-long mature region with neurite-inducing activity. From the poly(A)(+) RNA prepared from the producing fungal strain, a cDNA fragment encoding the mature region of p15 was amplified and His(6)-tagged recombinant p15 was produced in Escherichia coli. The recombinant protein purified by a single step on Ni(2+) agarose column chromatography exhibited comparable specific activity as native p15 in the PC12 neurite extension assay. The effect of His(6)-p15 was blocked by nicardipine, suggesting that Ca(2+) influx through the L-type Ca(2+) channels is essential for its neurite-inducing activity. In addition, mutational analysis of His(6)-p15 demonstrated that both intramolecular disulfide bonds are essential for its biological activity.

Intranodal benign thyroid tissue: significance of HBME-1 in differentiation from metastatic papillary thyroid carcinoma

The aim of this study was to determine the significance of HBME-1 immunostaining in the differentiation between intranodal benign thyroid tissue and metastatic papillary thyroid carcinoma in the lymph node. Immunohistochemically we examined normal-appearing intranodal thyroid tissue in four patients who did not show evidence of papillary carcinoma histologically or clinically. We also examined follicular-pattern-predominant papillary carcinoma with metastatic foci in the lymph nodes. Normal-appearing intranodal thyroid tissue and normal thyroid showed no immunopositivity for HBME-1. In contrast, all papillary carcinomas in both the lymph nodes and thyroid demonstrated strong positivity for HBME-1. HBME-1 was predominantly positive for the luminal surface of the tumor cells. The immunopositivity of the cuboidal and low columnar carcinoma cells was more intensive than that of the flat-shaped cells in the lymph nodes and thyroid. The results probably indicate that HBME-1 immunostaining is helpful in distinguishing between intranodal benign thyroid tissue and metastatic papillary carcinoma in lymph nodes. We emphasize that the HBME-1 reactivity should be evaluated in connection with the histological findings, and that positive and negative controls stained in parallel are necessary.

Abnormal venous structures in salivary gland tumors: vasculature characteristics of pleomorphic adenoma

To clarify the diagnostic significance of abnormal venous structures present in salivary gland tumors, we examined 21 pleomorphic adenomas, 14 Warthin tumors, 1 oncocytic adenoma, 3 myoepitheliomas, 7 basal cell adenomas, 5 mucoepidermoid carcinomas, and 6 adenoid cystic carcinomas. Verhoeffvan Gieson staining was carried out and the morphology of the veins within the tumors was observed microscopically. Branching veins, thickened intima of the veins, discontinuous elastic membrane and multilayered elastic membrane were seen in 71.4%, 76.2%, 47.6% and 85.7% of pleomorphic adenomas, respectively, and were abundant and easily found in most cases. The abnormal venous structures were also found in other salivary gland tumors examined, but they were few in number and lacked variety. Elastic fibers extending radially into the surrounding stroma were seen in 66.7% of pleomorphic adenomas, and were not seen in other salivary gland tumors. Our results showed that a variety of abnormal venous structures are more abundant and more easily found in pleomorphic adenoma compared with other salivary gland tumors, and, in particular, that perivascular radiating elastic fibers are characteristic of pleomorphic adenoma. We emphasize that the presence of perivascular radiating elastic fibers may be helpful in diagnosing pleomorphic adenoma in small biopsy specimens.

Purification, crystallization and preliminary X-ray diffraction analysis of the yeast Sec12Deltap protein, a guanine nucleotide-exchange factor involved in vesicle transport

Sec12 is a guanine nucleotide-exchange factor (GEF) of the GTP-binding protein Sar1. Its GEF activity on Sar1 makes it a key element in vesicle budding from the endoplasmic reticulum to the Golgi apparatus in yeast. Sec12 is an integral membrane glycoprotein of 70 kDa. A 38.5 kDa N-cytoplasmic domain (Sec12Deltap) has been expressed in Saccharomyces cerevisiae and in Escherichia coli, purified to homogeneity and crystallized. Two crystal forms were obtained. Crystal form I belongs to space group P6(2)/P6(4), with unit-cell parameters a = b = 191.7, c = 53.3 A, gamma = 120 degrees, and diffracts to 2.6 A resolution. Crystal form II belongs to space group P1, with unit-cell parameters a = 52.6, b = 53.0, c = 116.8 A, alpha = 98.0, beta = 97.4, gamma = 93.4 degrees, and diffracts to 2.0 A resolution.

Phosphorylation of cofilin by LIM-kinase is necessary for semaphorin 3A-induced growth cone collapse

Semaphorin 3A is a chemorepulsive axonal guidance molecule that depolymerizes the actin cytoskeleton and collapses growth cones of dorsal root ganglia neurons. Here we investigate the role of LIM-kinase 1, which phosphorylates an actin-depolymerizing protein, cofilin, in semaphorin 3A-induced growth cone collapse. Semaphorin 3A induced phosphorylation and dephosphorylation of cofilin at growth cones sequentially. A synthetic cell-permeable peptide containing a cofilin phosphorylation site inhibited LIM-kinase in vitro and in vivo, and essentially suppressed semaphorin 3A-induced growth cone collapse. A dominant-negative LIM kinase, which could not be activated by PAK or ROCK, suppressed the collapsing activity of semaphorin 3A. Phosphorylation of cofilin by LIM-kinase may be a critical signaling event in growth cone collapse by semaphorin 3A.

Roles of Meltrin beta /ADAM19 in the processing of neuregulin

Meltrin beta/ADAM19 is a member of ADAMs (a disintegrin and metalloproteases), which are a family of membrane-anchored glycoproteins that play important roles in fertilization, myoblast fusion, neurogenesis, and proteolytic processing of several membrane-anchored proteins. The expression pattern of meltrin beta during mouse development coincided well with that of neuregulin-1 (NRG), a member of the epidermal growth factor family. Then we examined whether meltrin beta participates in the proteolytic processing of membrane-anchored NRGs. When NRG-beta1 was expressed in mouse L929 cells, its extracellular domain was constitutively processed and released into the culture medium. This basal processing activity was remarkably potentiated by overexpression of wild-type meltrin beta, which lead to the significant decrease in the cell surface exposure of extracellular domains of NRG-beta1. Furthermore, expression of protease-deficient mutants of meltrin beta exerted dominant negative effects on the basal processing of NRG-beta1. These results indicate that meltrin beta participates in the processing of NRG-beta1. Since meltrin beta affected the processing of NRG-beta4 but not that of NRG-alpha2, meltrin beta was considered to have a preference for beta-type NRGs as substrate. Furthermore, the effects of the secretory pathway inhibitors suggested that meltrin beta participates in the intracellular processing of NRGs rather than the cleavage on the cell surface.

Cross-talk and ammonia channeling between active centers in the unexpected domain arrangement of glutamate synthase

INTRODUCTION

The complex iron-sulfur flavoprotein glutamate synthase catalyses the reductive synthesis of L-glutamate from 2-oxoglutarate and L-glutamine, a reaction in the plant and bacterial pathway for ammonia assimilation. The enzyme functions through three distinct active centers carrying out L-glutamine hydrolysis, conversion of 2-oxoglutarate into L-glutamate, and electron uptake from an electron donor.

RESULTS

The 3.0 A crystal structure of the dimeric 324 kDa core protein of a bacterial glutamate synthase was solved by the MAD method, using the very weak anomalous signal of the two 3Fe-4S clusters present in the asymmetric unit. The 1,472 amino acids of the monomer fold into a four-domain architecture. The two catalytic domains have canonical Ntn-amidotransferase and FMN binding (beta/alpha)8 barrel folds, respectively. The other two domains have an unusual "cut (beta/alpha)8 barrel" topology and an unexpected novel beta-helix structure. Channeling of the ammonia intermediate is brought about by an internal tunnel of 31 A length, which runs from the site of L-glutamine hydrolysis to the site of L-glutamate synthesis.

CONCLUSIONS

The outstanding property of glutamate synthase is the ability to coordinate the activity of its various functional sites to avoid wasteful consumption of L-glutamine. The structure reveals two polypeptide segments that connect the catalytic centers and embed the ammonia tunnel, thus being ideally suited to function in interdomain signaling. Depending on the enzyme redox and ligation states, these signal-transducing elements may affect the active site geometry and control ammonia diffusion through a gating mechanism.

Crystal structure of 1-aminocyclopropane-1-carboxylate deaminase from Hansenula saturnus

The pyridoxal 5'-phosphate (PLP)-dependent enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACCD) catalyzes a reaction that involves a ring opening of cyclopropanoid amino acid, yielding alpha-ketobutyrate and ammonia. Unlike other PLP-dependent enzymes, this enzyme has no alpha-hydrogen atom in the substrate. Thus, a unique mechanism for the bond cleavage is expected. The crystal structure of ACCD from Hansenula saturnus has been determined at 2.0 A resolution by the multiple wavelength anomalous diffraction method using mercury atoms as anomalous scatterers. The model was built on the electron density map, which was obtained by the density averaging of multiple crystal forms. The final model was refined to an R-factor of 22.5% and an R(free)-factor of 26.8%. The ACCD folds into two domains, each of which has an open twisted alpha/beta structure similar to the beta-subunit of tryptophan synthase. However, in ACCD, unlike in other members of the beta family of PLP-dependent enzymes, PLP is buried deep in the molecule. The structure provides the first view of the catalytic center of the cyclopropane ring opening.

Dilated rough endoplasmic reticulum corresponding to septate cytoplasmic vacuoles in papillary thyroid carcinoma

Septate cytoplasmic vacuoles, which are one of the cytologic findings characteristic of papillary thyroid carcinoma, are small, uniform, and well-defined vacuoles, with defined strands of cytoplasm separating them. We report on a case with histologic and ultrastructural findings corresponding to septate cytoplasmic vacuoles, which have not been previously described. The patient was a 51-yr-old man with a mass in the left anterior of the neck, measuring 4.0 x 3.5 cm in diameter. Aspiration cytology smears revealed findings typical of papillary thyroid carcinoma, including papillary tissue fragments, intranuclear inclusions, nuclear grooves, powdery chromatin, and psammoma bodies. The tumor cells which were located at the periphery of small three-dimensional clusters, and others which showed a sheet-like arrangement, demonstrated uniform, small vacuoles in relatively abundant, dense cytoplasm. Histologically, a small number of papillary thyroid carcinoma cells with multiple vacuoles were observed, which were limited to the hobnail-shaped cells located at papillary configurations or floating tumor cells within the papillary lumen. Ultrastructurally, the hobnail-shaped tumor cells demonstrated various-sized dilated rough endoplasmic reticulum and rich heterochromatin. We emphasize that septate cytoplasmic vacuoles correspond to dilated rough endoplasmic vacuoles and are probably related to degenerative changes.

Hypersegmentation of inflammatory cells in Langerhans cell granulomatosis

Langerhans cell granulomatosis (LCG) is characterized by a mixture of Langerhans cells and eosinophils in varying proportions. The characteristic morphology of Langerhans cells have already been described in many articles, but little attention has been paid to inflammatory cells. We examined six cases of Langerhans cell granulomatosis, which had originally been diagnosed as eosinophilic granuloma. Inflammatory cells present in LCG showed hypersegmentation. Twenty percent to 70% of eosinophils had three or more segmented nuclei, and 10-25% of neutrophils had five or more segmented nuclei. Such findings have never been described, and we believe hypersegmentation to be a feature of LCG. Furthermore, we emphasize that eosinophils in LCG mimic neutrophils in ethanol-fixed preparations, and thus may be a pitfall in making a diagnosis in cytology and intraoperative consultation.

Gastrointestinal stromal tumor with skeinoid fibers of the ileum

Gastrointestinal stromal tumor (GIST) is not uncommon among gastrointestinal nonepithelial tumors, but there are few reports describing the cytologic findings. We report a case of GIST with skeinoid fibers in scrape cytology preparation. The patient was a 53-year-old man with a tumor in the small intestine. Scrape preparations from the cut surface of the resected tumor revealed cellular material composed of spindle cells showing loose clusters or single cells. The nuclei were spindled, elongated or cigar-shaped, and relatively uniform. The cytoplasm was fragile and demonstrated a finely fibrillar material. Dense hyaline materials with irregular outline were observed within the loose clusters composed of the tumor cells. The hyaline materials were also observed in the background. Histologic preparation showed spindle cells arranged in a fascicular or storiform pattern. Most eosinophilic globules were distributed between the tumor cells. The globules were positive in periodic acid-Schiff reaction, and were stained blue with Masson's trichrome stain. Immunohistochemically, the tumor cells were strongly and diffusely positive for c-kit, focally and weakly positive for alpha-smooth muscle actin, and negative for CD34 and S-100 protein. We emphasize that skeinoid fibers are characteristic of GIST arising in the small intestine, and their presence predicts a good prognosis, even in malignant GIST.

Ovarian fibrothecoma with massive edema

We report a rare case of ovarian fibrothecoma with massive edema. The patient was a 59-year-old woman with a left ovarian mass measuring 11 x 10 x 7 cm. Magnetic resonance images revealed a solid mass showing unhomogeneous content with predominantly high signal intensity on T2-weighted image. Microscopically, the ovarian mass was composed of a cellular area and an edematous hypocellular area. The latter accounted for more than 75% of the tumor. In the cellular area, spindle-shaped or plump tumor cells were randomly distributed or arranged in a fascicular fashion. These cells contained abundant intracytoplasmic lipid. There was dense collagenous connective tissue in the stroma of the cellular areas. In contrast, in the edematous areas spindle or stellate cells were scattered. Alcian blue stain revealed only a small amount of stromal mucin even in the edematous areas. The microscopic findings were consistent with that of fibrothecoma with massive edema. The present case must be differentiated from massive edema of the ovary and sclerosing stromal tumor of the ovary. Immunohistochemistry was not helpful in distinguishing them. The age of the patient and careful histologic observation are important.

Vasitis nodosa: immunohistochemical findings--case report

We report the immunohistochemical features of vasitis nodosa and discuss the differential diagnosis. The patient was a 42-year-old Japanese man with bilateral small indurations of the vas deferens at the site of a previous vasectomy. Microscopically, small-sized ducts proliferated within the muscular wall of the vas deferens, and focally in the surrounding connective tissue. Immunohistochemically, most proliferating glandular cells were strongly positive for cytokeratins 7, 19, and 34betaE12, and vimentin. Epithelial membrane antigen and Leu-M1 reacted against the luminal surface of the cells. Focally, glandular cells were also positive for CA125. Cytokeratin 20, carcinoembryonic antigen, and prostate-specific antigen were negative. We discuss the immunohistochemical differentiation of vasitis nodosa from prostatic adenocarcinoma, adenocarcinoma of the rete testis, and adenomatoid tumor.

Well-differentiated adenocarcinoma of the gallbladder mimicking minimal deviation adenocarcinoma of the cervix

We report a case of well-differentiated adenocarcinoma of the gallbladder, histologically mimicking minimal deviation adenocarcinoma (MDA) of the cervix. A 71-year-old Japanese male underwent cholecystectomy because of the suggestion of gallbladder carcinoma. The resected gallbladder showed a localized thickening of the gallbladder wall with a polypoid lesion measuring 12x7 mm in diameter. Microscopically, the polypoid lesion proved to be a well-differentiated adenocarcinoma composed of columnar cells with a clear cytoplasm. In the thickened gallbladder wall, well-formed glands were extensively distributed; they were surrounded by a slightly desmoplastic reaction instead of lamina propria, or were directly in contact with smooth muscle cells. The diagnostic criteria for cervical MDA may be useful in distinguishing well-differentiated adenocarcinoma of the gallbladder from benign conditions, such as Rokitansky-Aschoff sinus and adenomyomatosis. It is remarkable that the tumor cells of the present case expressed gastric type mucin which is characteristic of mucinous type cervical MDA.

Altered expression of beta-catenin in renal cell cancer and transitional cell cancer with the absence of beta-catenin gene mutations

Loss of normal beta-catenin expression and the beta-catenin gene mutations have been shown to contribute to the malignant character of various cancers. Using PCR-single-strand conformation polymorphism and DNA direct sequencing, we examined the presence of genetic alterations within the third exon of beta-catenin, which are frequently observed in other tumors, in transitional cell cancer (TCC) and renal cell cancer (RCC) cell lines, and in tumor specimens. The degrees of expression and intracellular distribution of beta-catenin were detected by immunohistochemical staining in 77 primary and 12 metastatic RCCs and in 81 primary TCCs. Western blot analysis was also applied to confirm the degree of beta-catenin expression in the cell lines and some tumor samples. We failed to reveal any genetic alterations, at least in the third exon of the beta-catenin gene, in RCC and TCC. Reduced membranous immunoreactivity of beta-catenin was observed in portions of RCC (15.5%) and TCC (24.7%) and was correlated with advanced stages and nodal involvement in RCC and with advanced stages and multiple tumors in TCC. Within the power limitations of this small study, beta-catenin abnormal expression was not correlated with recurrence or survival in either RCC or TCC. Interstitial deletions and mutations in the third exon of beta-catenin do not play a significant role in RCC or TCC tumorigenesis. Down-regulation of normal beta-catenin expression might contribute to the malignant character of RCC and TCC and result in tumor progression. However, this event is not an independent prognostic factor for recurrence or tumor specific survival.

Characterization of a novel fungal protein, p15, which induces neuronal differentiation of PC12 cells

In our previous paper, we reported that a 15 kDa protein (p15) produced by a fungus, genus Helicosporium, enhanced NGF-induced neurite outgrowth from PC12 cells. Here we further characterized the actions of p15. The complete amino acid sequence of p15 was determined and it was shown to be a hydrophilic protein composed of 118 amino acid residues with two intramolecular disulfide bridges. p15-induced neurite outgrowth was blocked by the depletion of extracellular Ca(2+) in the culture medium and was significantly inhibited by L-type Ca(2+) channel inhibitor nicardipine. p15 stimulated Src kinase and MAPK activities, and neurite outgrowth was not observed in srcDN2, a dominant negative c-src(K295R)-expressing cell line, and was significantly reduced in RasN17-expressing cells. These results suggest that p15 stimulates neurite outgrowth through the potentiation of L-type Ca(2+) channels, thereby activating the Src-Ras-MAPK cascade.

Fas ligand-induced apoptosis of hepatocytes in natural killer cell leukaemia

Neoplastic natural killer (NK) cells overexpress Fas ligand (FasL), which may cause damage of Fas-bearing tissues. We report a patient with NK cell leukaemia who developed liver injury after pharyngitis. The NK leukaemic cells expressed functional FasL. In addition to soluble FasL, serum levels of interleukin-6 and interferon-gamma were increased dramatically when liver injury was aggravated. Moreover, hepatocytes expressed Fas and apoptotic hepatocytes were detected in the portal areas. These findings are consistent with the notion that inflammatory cytokines enhance the sensitivity to FasL and trigger apoptosis of hepatocytes in NK cell malignancies.

Bladder neck suspension using percutaneous bladder neck stabilization to the pubic bone with a bone-anchor suture fixation system: A new extraperitoneal laparoscopic approach

A 39-year-old woman with type 1 genuine stress urinary incontinence was treated using a novel extraperitoneal laparoscopic bladder neck suspension procedure with a bone-anchor suture fixation system. Operative time and blood loss were 2.5 and 50 g, respectively. The patient showed a remarkable improvement on chain cystography and in subjective and objective well-being with no complications, even 12 months after surgery. Extraperitoneal laparoscopic bladder neck suspension using the bone-anchor suture fixation system is an easy and feasible procedure.

Structure of tropinone reductase-II complexed with NADP+ and pseudotropine at 1.9 A resolution: implication for stereospecific substrate binding and catalysis

Tropinone reductase-II (TR-II) catalyzes the NADPH-dependent reduction of the carbonyl group of tropinone to a beta-hydroxyl group. The crystal structure of TR-II complexed with NADP+ and pseudotropine (psi-tropine) has been determined at 1.9 A resolution. A seven-residue peptide near the active site, disordered in the unliganded structure, is fixed in the ternary complex by participation of the cofactor and substrate binding. The psi-tropine molecule is bound in an orientation which satisfies the product configuration and the stereochemical arrangement toward the cofactor. The substrate binding site displays a complementarity to the bound substrate (psi-tropine) in its correct orientation. In addition, electrostatic interactions between the substrate and Glu156 seem to specify the binding position and orientation of the substrate. A comparison between the active sites in TR-II and TR-I shows that they provide different van der Waals surfaces and electrostatic features. These differences likely contribute to the correct binding mode of the substrates, which are in opposite orientations in TR-II and TR-I, and to different reaction stereospecificities. The active site structure in the TR-II ternary complex also suggests that the arrangement of the substrate, cofactor, and catalytic residues is stereoelectronically favorable for the reaction.

Biclonal lymphoplasmacytic immunocytoma associated with Crohn's disease

A 33-year-old man with a 4-year history of Crohn's disease presented with marked ascites and an abdominal tumor. Two M-protein peaks, immunoglobulin (Ig) G-kappa and IgA-kappa, were detected in the serum. Neoplastic lymphoplasmacytic cells were infiltrated in the bone marrow and ascites. Histological examination of the abdominal tumor showed marked proliferation of lymphoplasmacytic cells that were positive for either IgG or IgA. Moreover, DNA sequences of the expressed IgG and IgA genes were different in the complementarity-determining region 3. These results suggest that chronic inflammation in Crohn's disease contributes to the simultaneous development of biclonal lymphoplasmacytic immunocytoma of the small intestine.