EBF1-JAK2 inhibits the PAX5 function through physical interaction with PAX5 and kinase activity

Gene aberrations of B-cell regulators and growth signal components such as the JAK-STAT pathway are frequently found in B-cell acute lymphoblastic leukemia (B-ALL). EBF1 is a B-cell regulator that regulates the expression of PAX5 and co-operates with PAX5 to regulate B-cell differentiation. Here, we analyzed the function of the fusion protein of EBF1 and JAK2, EBF1-JAK2 (E-J). E-J caused constitutive activation of JAK-STAT and MAPK pathways and induced autonomous cell growth in a cytokine-dependent cell line. E-J did not affect the transcriptional activity of EBF1 but inhibited that of PAX5. Both the physical interaction of E-J with PAX5 and kinase activity of E-J were required for E-J to inhibit PAX5 function, although the detailed mechanism of inhibition remains unclear. Importantly, gene set enrichment analysis using the results of our previous RNA-seq data of 323 primary BCR-ABL1-negative ALL samples demonstrated repression of the transcriptional target genes of PAX5 in E-J-positive ALL cells, which suggests that E-J also inhibited PAX5 function in ALL cells. Our results shed new light on the mechanisms of differentiation block by kinase fusion proteins.

Functional inhibition of MEF2 by C/EBP is a possible mechanism of leukemia development by CEBP-IGH fusion gene

CEBPA-IGH, a fusion gene of the immunoglobulin heavy-chain locus (IGH) and the CCAAT enhancer-binding protein α (C/EBPα) gene, is recurrently found in B-ALL cases and causes aberrant expression of C/EBPα, a master regulator of granulocyte differentiation, in B cells. Forced expression of C/EBPα in B cells was reported to cause loss of B-cell identity due to the inhibition of Pax5, a master regulator of B-cell differentiation; however, it is not known whether the same mechanism is applicable for B-ALL development by CEBPA-IGH. It is known that a full-length isoform of C/EBPα, p42, promotes myeloid differentiation, whereas its N-terminal truncated isoform, p30, inhibits myeloid differentiation through the inhibition of p42; however, the differential role between p42 and p30 in ALL development has not been clarified. In the present study, we examined the effect of the expression of p42 and p30 in B cells by performing RNA-seq of mRNA from LCL stably transfected with p42 or p30. Unexpectedly, suppression of PAX5 target genes was barely observed. Instead, both isoforms suppressed the target genes of MEF2 family members (MEF2s), other regulators of B-cell differentiation. Similarly, MEF2s target genes rather than PAX5 target genes were suppressed in CEBP-IGH-positive ALL (n = 8) compared with other B-ALL (n = 315). Furthermore, binding of both isoforms to MEF2s target genes and the reduction of surrounding histone acetylation were observed in ChIP-qPCR. Our data suggest that the inhibition of MEF2s by C/EBPα plays a role in the development of CEBPA-IGH-positive ALL and that both isoforms work co-operatively to achieve it.

Unraveling unique features of plasma cell clones in POEMS syndrome by single-cell analysis

POEMS syndrome is a rare monoclonal plasma cell disorder with unique symptoms distinct from other plasma cell neoplasms, including high serum VEGF levels. Since the prospective isolation of POEMS clones has not yet been successful, their real nature remains unclear. We herein performed the single-cell RNA sequencing of bone marrow plasma cells from patients with POEMS syndrome and identified POEMS clones that had immunoglobulin λ light chain (IGL) sequences (IGLV1-36, 40, 44, and 47) with amino acid changes specific to POEMS syndrome. The proportions of POEMS clones in plasma cells were markedly smaller (median: 12.9%) than in multiple myeloma (MM) (96-100%) and monoclonal gammopathy of undetermined significance (MGUS) patients (57-81%). Single-cell transcriptomes revealed that POEMS clones were CD19-negative, CD138-positive, and MHC class II-low, which allowed for their prospective isolation. POEMS clones expressed significantly lower levels of c-MYC and CCND1 than MM, accounting for their small size. VEGF mRNA was not up-regulated in POEMS clones, directly indicating that VEGF is not produced by POEMS clones. These results reveal unique features of POEMS clones and enhance our understanding of the pathogenesis of POEMS syndrome.

High prevalence of myeloid malignancies in progeria with Werner syndrome is associated with p53 insufficiency

Werner syndrome (WS) is a progeroid syndrome caused by mutations in the WRN gene, which encodes the RecQ type DNA helicase for the unwinding of unusual DNA structures and is implicated in DNA replication, DNA repair, and telomere maintenance. WS patients are prone to develop malignant neoplasms, including hematological malignancies. However, the pathogenesis of WS-associated hematological malignancies remains uncharacterized. Here we investigated the somatic gene mutations in WS-associated MDS/AML. Whole-exome sequencing (WES) of 4 WS patients with MDS/AML revealed that all patients had somatic mutations in TP53 but no other recurrent mutations in MDS/AML. TP53 mutations were identified at low allele frequencies at more than one year before the MDS/AML stage. All 4 patients had complex chromosomal abnormalities including those that involved TP53. Targeted sequencing of 9 WS patients without apparent blood abnormalities did not detect recurrent mutations in MDS/AML except for a PPM1D mutation. These results suggest that WS patients are apt to acquire TP53 mutations and/or chromosomal abnormalities involving TP53, rather than other MDS/AML-related mutations. TP53 mutations are frequently associated with prior exposure to chemotherapy; however, all 4 WS patients with TP53 mutations/deletions had not received any prior chemotherapy, suggesting a pathogenic link between WRN mutations and p53 insufficiency. These results indicate that WS hematopoietic stem cells with WRN insufficiency acquire competitive fitness by inactivating p53, which may cause complex chromosomal abnormalities and the subsequent development of myeloid malignancies. These findings promote our understanding of the pathogenesis of myeloid malignancies associated with progeria.

Exosomes secreted from cancer-associated fibroblasts elicit anti-pyrimidine drug resistance through modulation of its transporter in malignant lymphoma

The tumor microenvironment is deeply involved in the process of tumor growth and development. In this study, we focused on cancer-associated fibroblasts (CAFs) and their derived exosomes on the lymphoma microenvironment to uncover their clinical significance. CAFs were established from primary lymphoma samples, and exosomes secreted from CAFs were obtained by standard procedures. We then investigated the roles of CAFs and their derived exosomes in the survival and drug resistance of lymphoma cells. CAFs supported the survival of lymphoma cells through increased glycolysis, and the extent differed among CAFs. Exosomes were identified as a major component of the extracellular vesicles from CAFs, and they also supported the survival of lymphoma cells. The suppression of RAB27B, which is involved in the secretion of exosomes, using a specific siRNA resulted in reduced exosome secretion and decreased survival of lymphoma cells. Moreover, anti-pyrimidine drug resistance was induced in the presence of exosomes through the suppression of the pyrimidine transporter, equilibrative nucleoside transporter 2 (ENT2), and the suppression of ENT2 was significant in in vivo experiments and clinical samples. RNA sequencing analysis of miRNAs in exosomes identified miR-4717-5p as one of the most abundant miRNAs in the exosome, which suppressed the expression of ENT2 and induced anti-pyrimidine drug resistance in vitro. Our results suggest that exosomes including miR-4717-5p secreted from CAFs play a pivotal role in the lymphoma microenvironment, indicating that they are a promising therapeutic target.

Abstract P2-18-11: A multi-center prospective study of image-guided radiofrequency ablation for small breast carcinomas

Background: As the management of breast carcinoma evolves toward less invasive treatments, the next step is the possibility of removing the primary tumor without surgery. The most promising noninvasive ablation technique is radiofrequency ablation (RFA), which can effectively kill tumor cells with a low complication rate. Our preliminary studies of RFA followed by standard surgical resection have indicated that this technique is effective for surgical ablation of small (≤ 2cm) breast tumors without extensive intraductal components (EIC).

Methods: To determine if RFA is oncologically and cosmetically appropriate for the local treatment of primary breast carcinoma, this multi-center prospective study used RFA as the sole local treatment of breast tumors ≤ 1.5cm in size on ultrasound and MRI. Exclusion criteria include receiving of preoperative chemotherapy, or the presence of invasive lobular carcinoma or invasive ductal carcinoma with suspicious EIC. After confirmation that the standard baseline core biopsy for diagnosis and measurement of tumors markers (ER, PgR, HER-2/neu expression and the presence of the Ki-67 proliferative marker) have been obtained, consent will be obtained and the patient scheduled RFA. All patients received adjuvant radiation therapy. The use and choice of systemic therapy will be based on the information from the baseline core biopsy and imaging studies. The first primary endpoints of this study is successful tumor ablation, as evidenced by negative findings on vacuum-assisted or core biopsies and imaging studies after RFA. The second primary endpoints is the incidence of procedure related adverse events. Forty patients with small tumors that are clearly identifiable and measurable by ultrasound and MRI were enrolled. The response to ablation was evaluated with both vacuum-assisted or core biopsies and imaging studies every 3 months during the first year. The long-term outcomes were assessed using quality of life measurement scales and imaging studies every 6 months thereafter through year 5.

Results: Of the 58 patients who participated in this study, 55 completed the protocol. In 50 of the 55 (91%) treated patients, successful tumor ablation, as determined by negative findings on vacuum-assisted or core biopsies and imaging studies, was confirmed. In these 50patients, there were no local or distant recurrences after 1 year. The remaining 5 patients with biopsies positive for residual tumor underwent surgical resection. In 46 of the 50 patients with successful ablation, cosmetic outcomes were excellent after 1 year and only 2 patients experienced minor skin burns during the tumor ablation. No other adverse events were reported.

Conclusions: RFA can be safely used alone in patients with small breast tumors, provided that local tumor control must be regularly assessed by image-guided vacuum-assisted or core biopsies after ablation. RFA in patients with early breast carcinoma can achieve local control rates similar to those with wide local excision, but with improved cosmetic results.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-18-11.

Identification of a 3.7-Mb region for a marbling QTL on bovine chromosome 4 by identical-by-descent and association analysis

QTL mapping for growth and carcass traits was performed using a paternal half-sib family composed of 325 Japanese Black cattle offspring. Nine QTL were detected at the 1% chromosome-wise significance level at a false discovery rate of less than 0.1. These included two QTL for marbling on BTA 4 and 18, two QTL for carcass weight on BTA 14 and 24, two QTL for longissimus muscle area on BTA 1 and 4, two QTL for subcutaneous fat thickness on BTA 1 and 15 and one QTL for rib thickness on BTA 6. Although the marbling QTL on BTA 4 has been replicated with significant linkages in two Japanese Black cattle sires, the three Q (more marbling) haplotypes, each inherited maternally, were apparently different. To compare the three Q haplotypes in more detail, high-density microsatellite markers for the overlapping regions were developed within the 95% CIs (65 markers in 44-78 cM). A detailed haplotype comparison indicated that a small region (<3.7 Mb) around 46 cM was shared between the Qs of the two sires, whose dams were related. An association of this region with marbling was shown by a regression analysis using the local population, in which the two sires were produced and this was confirmed by an association study using a population collected throughout Japan. These results strongly suggest that the marbling QTL on BTA 4 is located in the 3.7-Mb region at around 46 cM.

Relationship of the bovine growth hormone gene to carcass traits in Japanese black cattle

The bovine growth hormone gene (bGH) possesses three haplotypes, A, B and C, that differ by amino acid mutations at positions 127 and 172 in the fifth exon: (leucine 127, threonine 172), (valine 127, threonine 172) and (valine 127, methionine 172) respectively. The correlation between meat quality or carcass weight and these haplotypes was investigated in Japanese black cattle. Altogether, 940 bGH haplotypes were compared with respect to six carcass traits: carcass weight, longissimus muscle area, rib thickness, subcutaneous fat thickness, beef marbling score and beef colour. The frequency of the B haplotype was higher (0.421) than that of A (0.269) and C (0.311). High carcass weight and low beef marbling were associated with haplotype A (p < 0.05 and p < 0.01 respectively), whereas beef marbling was increased by haplotype C (p < 0.05). Estimated regression coefficient of the A haplotype substitution effect for carcass weight and beef marbling score were 5.55 (13.1% of the phenotypic SD) and -0.31 (17.0%) respectively. That of the C haplotype for beef marbling score was 0.20 (11.0%). The other traits showed no relationship to the haplotypes examined. The results of this investigation suggest that information pertaining to bGH polymorphisms in Japanese black cattle could be used to improve the selection of meat traits.

Mapping of quantitative trait loci for carcass traits in a Japanese Black (Wagyu) cattle population

To detect quantitative trait loci (QTL) that influence economically important traits in a purebred Japanese Black cattle population, we performed a preliminary genome-wide scan using 187 microsatellite markers across a paternal half-sib family composed of 258 offspring. We located six QTL at the 1% chromosome-wise level on bovine chromosomes (BTA) 4, 6, 13, 14 and 21. A second screen of these six QTL regions using 138 additional paternal offspring half-sib from the same sire, provided further support for five QTL: carcass weight on BTA14 (22-39 cM), one for rib thickness on BTA6 (27-58 cM) and three for beef marbling score (BMS) on BTA4 (59-67 cM), BTA6 (68-89 cM) and BTA21 (75-84 cM). The location of QTL for subcutaneous fat thickness on BTA13 was not supported by the second screen (P > 0.05). We determined that the combined contribution of the three QTLs for BMS was 10.1% of the total variance. The combined phenotypic average of these three Q was significantly different (P < 0.001) from those of other allele combinations. Analysis of additional half-sib families will be necessary to confirm these QTL.

Frequent overexpression of epidermal growth factor receptor (EGFR) in mammary high grade ductal carcinomas with myoepithelial differentiation

AIMS

To evaluate the expression of common biological markers and the epidermal growth factor receptor (EGFR) in mammary high grade ductal carcinomas with myoepithelial differentiation (DCMDs).

MATERIALS/METHODS

Thirty DCMDs were clinicopathologically and immunohistochemically analysed and compared with 36 control cases of high grade conventional invasive ductal carcinoma (IDC).

RESULTS

EGFR, HER2/neu, oestrogen receptor, progesterone receptor, and p53 expression was seen in 21, one, three, four, and 20 of the 30 DCMDs, compared with eight, nine, 18, 17, and five of the 36 conventional IDCs (p<0.05), respectively. In 16 of the 30 DCMDs, metastases were found in the brain, lung, bone, and liver, within a maximum of 47 months (mean, 13.9) after initial surgery, whereas only four of the 36 conventional IDCs metastasised to the lung and bone within a maximum of 27 months (mean, 18.0) after initial surgery (p=0.0001). There was a significant difference in disease free survival between DCMD and conventional IDC (p=0.001). EGFR was frequently overexpressed in DCMD compared with conventional IDC, whereas the expression of HER2/neu and hormone receptors was lower in DCMD. Fluorescent in situ hybridisation revealed that the mean EGFR to chromosome 7 centromere (CEP7) ratio of the 24 DCMD cases available for evaluation was 1.03, and EGFR gene amplification was not detected in the 21 DCMD cases with EGFR overexpression.

CONCLUSION

Immunohistochemistry for myoepithelial markers and EGFR is useful for the accurate diagnosis and molecular target treatment of high grade DCMD.

Effects of styrene monomer and trimer on gonadal sex differentiation of genetic males of the frog Rana rugosa

To ascertain whether styrene monomer and trimer induce an estrogen-like effect, all-male tadpoles of Rana rugosa were exposed to dilute solutions of styrene monomer and trimer (2,4,6-tripfenyl-1-hexene) at concentrations of 0.1, 1, or 10 microM during days 19-23 after fertilization, which is the critical period of gonadal sex differentiation. As positive and vehicle controls, tadpoles were exposed to dilute solutions of estradiol-17beta at concentrations of 0.01, 0.1, or 1 microM and 0.01% ethanol, respectively, during the same period. The influence was estimated by examining the inner structure of the gonads of 40-day-old tadpoles. All the gonads of tadpoles in the vehicle and untreated controls showed histological characteristics of testes, whereas all those of tadpoles treated with 1 microM estradiol-17beta showed a structure typical for ovaries, having an ovarian sac and many meiotic germ cells. Of the genetically male tadpoles treated with styrene monomer and trimer, 97 and 96%, respectively, showed normal testicular structure of the gonads. In contrast, the remaining tadpoles had gonads showing coexistence of testicular and ovarian structure, irrespective of the strength of styrene concentration. These findings suggest that the styrene monomer and trimer induced a weak estrogen-like effect on the pathways of testicular differentiation in genetically male tadpoles.

Generation and characterization of a fairly stable triplet carbene

Most molecules are held together by covalent bonds-electron pairs jointly shared by the two atoms that are linked by the bond. Free radicals, in contrast, have at least one unpaired electron. In the case of carbon-based radicals, the carbon atom at the radical centre no longer makes four bonds with other atoms as it would do in its normal, tetravalent state. The presence of unpaired electrons renders such radicals highly reactive, so they normally occur only as transient intermediates during chemical reactions. But the discovery by Gomberg in 1900 of triphenylmethyl, the first relatively stable free radical containing a central trivalent carbon atom, illustrated that radicals with suitable geometrical and electronic structures can be stable. Compounds containing a divalent carbon atom that uses only two of its four valence electrons for bonding are usually less stable than Gomberg-type radicals with trivalent carbon. Although the role of these so-called carbenes in chemical reactions has long been postulated, they were unambiguously identified only in the 1950s. More recently, stable carbenes have been prepared, but the singlet state of these molecules, with the two nonbonding valence electrons paired, means that they are not radicals. Carbenes in the second possible electronic state, the triplet state, are radicals: the two nonbonding electrons have parallel spins and occupy different orbitals. Here we report the preparation and characterization of a triplet carbene, whose half-life of 19 minutes at room temperature shows it to be significantly more stable than previously observed triplet carbenes.

Validation and problems of St-Gallen recommendations of adjuvant therapy for node-negative invasive breast cancer in Japanese patients

BACKGROUND

The objectives of this study were to confirm the favorable outcome of invasive breast cancer in Japanese patients without lymph node metastasis who did not receive adjuvant therapies and to validate the St-Gallen recommendations in this population.

METHODS

The subjects were a consecutive series of 920 node-negative invasive breast cancer patients who underwent surgery between 1987 and 1994 at our hospital. These patients did not receive adjuvant chemotherapy. Ten-year disease-free (DFS) and overall survival (OS) rates were analyzed by the St-Gallen risk categories (Minimal/Low, Intermediate, High).

RESULTS

The median age of the patients at surgery was 52 years and the median follow-up period of patients was 10.2 years. At 10 years, the respective DFS and OS rates of all patients were 84.6 and 86.7%. The DFS and OS of patients in the Minimal/Low risk category (25 patients) both showed 100%. The DFS and OS of patients in the Intermediate risk category (356 patients) showed 92.0 and 93.1%, respectively. The DFS and OS of patients in the High risk category (539 patients) showed 79.4 and 82.2%, respectively, indicating a significant difference between those in the Minimal/Intermediate risk category (381 patients) (p < 0.001, p < 0.001, respectively). The DFS and OS of patients who had one pathological lymph node metastasis (775 patients) showed 72.7 and 75.2%, respectively, which indicated a non-significant difference between those in the High risk category (381 patients) (p = 0.10). These data support the validation of adjuvant therapy for high-risk node-negative breast cancers in Japanese patients. However, quality control is needed to define the histological grade included in the risk categories.

CONCLUSION

Japanese patients with invasive breast cancer without lymph node metastasis showed a survival advantage compared with their Caucasian counterparts. However, patients in the High risk group as defined by St-Gallen recommendations should be indicated for adjuvant therapy.

Changes in epididymal protein anti-agglutinin on ejaculated boar spermatozoa during capacitation in vitro

This study is a detailed investigation of changes in epididymal protein anti-agglutinin on ejaculated boar spermatozoa during an incubation designed to promote capacitation in vitro. Ejaculated spermatozoa were collected from six mature boars, washed, and incubated to promote capacitation. Sperm samples were subjected to Western blotting-densitometric analyses, flow cytometry after immunostaining and immunocytochemical observation by indirect immunofluorescence. An antiserum to anti-agglutinin was raised in a rabbit by subcutaneous injection of a purified antigen, as described previously (Harayama et al. 1999). Western blotting-densitometric analyses revealed an approximate halving of the amount of sperm-bound anti-agglutinin during the first 45-min incubation, followed by a gradual decrease thereafter. Comparison between immunostained sperm samples by flow cytometry before and after incubation confirmed this decrease in sperm-bound anti-agglutinin during the incubation. Microscopic characterization established that this decrease occurred mainly on the acrosome. Supplementation with seminal plasma (5% or 10%, v/v) attenuated the decrease. These findings are consistent with the conclusion that a large portion of the anti-agglutinin bound to sperm acrosomes is released at an early stage of the capacitation process in vitro.

Effects of calcium and bicarbonate on head-to-head agglutination in ejaculated boar spermatozoa

The present study was conducted to reveal the effects of calcium and bicarbonate on the occurrence of head-to-head agglutination in ejaculated boar spermatozoa in vitro. Boar spermatozoa were washed and incubated in a modified Krebs-Ringer bicarbonate (mKRB) in a 37 degrees C CO2 incubator (5% CO2 in air) for 1-5 h. Before and after the incubation, aliquots of each sperm sample were fixed, smeared on glass slides, and stained with a phosphate-buffered solution of Giemsa to assess the percentages of head-to-head agglutinated spermatozoa. Before the incubation, only 5-12% of the spermatozoa were agglutinated. After the 1-h incubation, however, the percentage of head-to-head agglutinated spermatozoa rose to approximately 50%, followed by only minor increases thereafter. This rise was dependent on the concentrations of calcium chloride contained in the mKRB and was attenuated by the addition of 2 mM [ethylenebis(oxyethylenenitrilo)]tetra-acetic acid (EGTA) to the medium. Moreover, the replacement of sodium bicarbonate with 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (Hepes) in the medium and treatment with ruthenium red, which have both been shown previously to inhibit calcium uptake by boar spermatozoa, significantly reduced the rise. Based on these findings, it was concluded that extracellular calcium and bicarbonate are key factors regulating head-to-head agglutination in boar spermatozoa. The possible relationship between agglutinability and the fertilizing ability of boar spermatozoa is also discussed.

Effects of exercise training on the heart rate variability and QT dispersion of patients with acute myocardial infarction

Heart rate variability (HRV) reflects the autonomic tone of the heart, and QT dispersion reflects the regional inhomogeneity of ventricular repolarization. The purpose of the present study was to determine the effects of early exercise training on HRV and QT dispersion in patients with acute myocardial infarction (AMI). Forty patients (mean age: 59 years) with AMI were randomized to training rehabilitation (group Tr, n=20) or conventional rehabilitation (group C, n=20). Two weeks after AMI, group Tr underwent 10 min of exercise using a bicycle ergometer (80% of anaerobic threshold) twice a day. At the end of the second and fourth weeks, 12-lead and 24-h Holter ECGs were recorded. QT intervals were measured and corrected using Bazett's formula (QTc), and QTc dispersion (QTcd) was defined as the difference between maximum and minimum QTc. HRV was accessed by the high-frequency component (HF: 0.15-0.40 Hz) of the HRV power spectrum (parasympathetic activity) and the ratio of low frequency (0.04-0.15 Hz) to HF (L/H ratio: sympathetic activity). In group Tr, HF increased (82.5 to 131.1 ms2), the L/H ratio decreased (3.9 to 2.6), and QTcd decreased (77.2 to 57.2 ms). In group C, none of the indices changed. It was concluded that early exercise training improves sympathovagal balance and decreases QTcd, and may reduce the arrhythmogenic substrate following AMI.

Neutron generator at Hiroshima University for use in radiobiology study

A neutron generator (HIRRAC) for use in radiobiology study has been constructed at the Research Institute for Radiation Biology and Medicine, Hiroshima University (RIRBM). Monoenergetic neutrons of which energy is less than 1.3 MeV are generated by the 7Li(p,n)7 Be reaction at proton energies up to 3 MeV. The protons are accelerated by a Schenkel-type-accelerator and are bombared onto the 7Li-target. An apparatus for the irradiation of biological material such as mice, cultured cells and so on, was designed and will be manufactured. Neutron and gamma-ray dose rates were measured by paired (TE-TE and C-CO2) ionization chambers. Contamination of the gamma ray was less than about 6% when using 10-microns-thick 7Li as a target. Maximum dose rates for the tissue equivalent materials was 40 cGy/min at a distance of 10 cm from the target. Energy distributions of the obtained neutrons have been measured by a 3He-gas proportional counter. The monoenergetic neutrons within an energy region from 0.1 to 1.3 MeV produced by thin 7Li or 7LiF targets had a small energy spread of about 50 keV (1 sigma width of gaussian). The energy spread of neutrons was about 10% or less at an incident proton energy of 2.3 MeV. We found that HIRRAC produces small energy spread neutrons and at sufficient dose rates for use in radiobiology studies.

Interaction of caffeine with L-tryptophan: study by 1H nuclear magnetic resonance spectroscopy

The interaction of caffeine with L-tryptophan was investigated in aqueous solution adjusted to an ionic strength of 0.20, at pH 6.2, by using 1H NMR spectroscopy. Caffeine interacted with L-tryptophan at a molar ratio of 1:1 by parallel stacking. The thermodynamic parameters obtained for the complexation were as follows: delta G degree = -1.70 kcal/mol at 25 degrees C (K = 17.6 M-1), delta H degree = -3.7 kcal/mol, delta S degree = -6.7 eu. It was found that the driving force for parallel stacking is a combination of electrostatic, polarization, and dispersion interactions, and the contribution of hydrophobic bonding is not large. A possible stacking mode is postulated based on the complexation shifts and pi-electron charge distributions of caffeine and L-tryptophan.