The CH···HC interaction in biphenyl is a delocalized, molecular-wide and entirely non-classical interaction: Results from FALDI analysis.

In this study we aim to determine the origin of the electron density describing a CH···HC interaction in planar and twisted conformers of biphenyl. In order to achieve this, the fragment, atomic, localized, delocalized, intra- and inter-atomic (FALDI) decomposition scheme was utilized to decompose the density in the inter-nuclear region between the ortho-hydrogens in both conformers. Importantly, the structural integrity, hence also topological properties, were fully preserved as no 'artificial' partitioning of molecules was implemented. FALDI-based qualitative and quantitative analysis revealed that the majority of electron density arises from two, non-classical and non-local effects: strong overlap of ortho CH σ-bonds, and long-range electron delocalization between the phenyl rings and ortho carbons and hydrogens. These effects resulted in a delocalized electron channel, that is, a density bridge or a bond path in a QTAIM terminology, linking the H-atoms in the planar conformer. The same effects and phenomena are present in both conformers of biphenyl. We show that the CH···HC interaction is a molecular-wide event due to large and long-range electron delocalization, and caution against approaches that investigate CH···HC interactions without fully taking into account the remainder of the molecule.

No difference in survival after HLA mismatched versus HLA matched allogeneic stem cell transplantation in Ewing sarcoma patients with advanced disease.

Patients with advanced Ewing sarcoma (AES) carry a poor prognosis. Retrospectively, we analyzed 66 AES patients treated with allogeneic stem cell transplantation (allo-SCT) receiving HLA-mismatched (group A, n = 39) versus HLA-matched grafts (group B, n = 27). Median age at diagnosis was 13 years, and 15 years (range 3-49 years) at allo-SCT. The two groups did not differ statistically in distribution of gender, age, remission status/number of relapses at allo-SCT, or risk stratum. 9/39 (23%) group A versus 2/27 (7%) group B patients developed severe acute graft versus host disease (GvHD). Of patients alive at day 100, 7/34 (21%) group A versus 9/19 (47%) group B patients had developed chronic GvHD. In group A, 33/39 (85%) versus 20/27 (74%) group B patients died of disease and 1/39 (3%) versus 1/27 (4%) patients died of complications, respectively. Altogether 12/66 (18%) patients survived in CR. Median EFS 24 months after allo-SCT was 20% in both groups, median OS was 27% (group A) versus 17% (group B), respectively. There was no difference in EFS and OS in AES patients transplanted with HLA-mismatched versus HLA-matched graft in univariate and multivariate analyses. In this analysis, CR at allo-SCT is a condition for survival (p < 0.02).

Characterization of bonding modes in metal complexes through electron density cross-sections.

Qualitative inspection of molecular orbitals (MOs) remains one of the most popular analysis tools used to describe the electronic structure and bonding properties of transition metal complexes. In symmetric coordination complexes, the use of group theory and the symmetry-adapted linear combination (SALC) of fragment orbitals allows for a very accurate and informative interpretation of MOs, but the same procedure cannot be performed for asymmetric complexes, such as Schrock and Fischer carbenes. In this work, we present a straight-forward approach for classifying and quantifying MO contributions to a particular metal-ligand interaction. Our approach utilizes the topology of MO density contributions to a cross-section of an inter-nuclear region, and is computationally inexpensive and applicable to symmetric and asymmetric complexes alike. We also apply the same approach with similar decompositions using Natural Bond Orbitals (NBO) and the recently developed Fragment, Atomic, Localized, Delocalized and Interatomic (FALDI) density decomposition scheme. In particular, FALDI analysis provides additional insights regarding the multi-centric nature of metal-carbene bonds without resorting to expensive multi-reference calculations.

Molecular Orbitals Support Energy-Stabilizing "Bonding" Nature of Bader's Bond Paths.

Our MO-based findings proved a bonding nature of each density bridge (DB, or a bond path with an associated critical point, CP) on a Bader molecular graph. A DB pinpoints universal physical and net energy-lowering processes that might, but do not have to, lead to a chemical bond formation. Physical processes leading to electron density (ED) concentration in internuclear regions of three distinctively different homopolar H,H atom-pairs as well as classical C-C and C-H covalent bonds were found to be exactly the same. Notably, properties of individual MOs are internuclear-region specific as they (i) concentrate, deplete, or do not contribute to ED at a CP and (ii) delocalize electron-pairs through either in- (positive) or out-of-phase (negative) interference. Importantly, dominance of a net ED concentration and positive e--pairs delocalization made by a number of σ-bonding MOs is a common feature at a CP. This feature was found for the covalently bonded atoms as well as homopolar H,H atom-pairs investigated. The latter refer to a DB-free H,H atom-pair of the bay in the twisted biphenyl (Bph) and DB-linked H,H atom-pairs (i) in cubic Li4H4, where each H atom is involved in three highly repulsive interactions (over +80 kcal/mol), and (ii) in a weak attractive interaction when sterically clashing in the planar Bph.

Origin of Hydrocarbons Stability from a Computational Perspective: A Case Study of Ortho-Xylene Isomers.

It is shown herein that intuitive and text-book steric-clash based interpretation of the higher energy "in-in" xylene isomer (as arising solely from the repulsive CH⋅⋅⋅HC contact) with respect to the corresponding global-minimum "out-out" configuration (where the clashing C-H bonds are tilted out) is misleading. It is demonstrated that the two hydrogen atoms engaged in the CH⋅⋅⋅HC contact in "in-in" are involved in attractive interaction so they cannot explain the lower stability of this isomer. We have proven, based on the arsenal of modern bonding descriptors (EDDB, HOMA, NICS, FALDI, ETS-NOCV, DAFH, FAMSEC, IQA), that in order to understand the relative stability of "in-in" versus "out-out" xylenes isomers one must consider the changes in the electronic structure encompassing the entire molecules as arising from the cooperative action of hyperconjugation, aromaticity and unintuitive London dispersion plus charge delocalization based intra-molecular CH⋅⋅⋅HC interactions.

Quantifying individual (anti)bonding molecular orbitals' contributions to chemical bonding.

The shapes of molecular orbitals (MOs) in polyatomic molecules are often difficult for meaningful chemical interpretations. We report protocols to quantify contributions made by individual orbitals (molecular canonical and natural) of classical bonding, non-bonding or anti-bonding nature to (i) electron density into the inter-nuclear region and (ii) diatomic electron delocalization, DI(A,B). In other words, these protocols universally explain orbital's inputs to two fundamental and energy-lowering mechanisms of chemical bonding (interactions) and ease the chemical interpretation of their character in polyatomic molecules. They reveal that the MO and real-space density descriptions of the interactions are equivalent and, importantly, equally apply to all atom-pairs regardless if they are involved in a highly attractive or repulsive interaction. Hence, they not only remove ambiguity in chemical bonding interpretations (based on either MO or electron density approaches) but also demonstrate complementarity between the two such seemingly different techniques. Finally, our approach challenges some classical assumptions about MOs, such as the role of core electrons, the degree of bonding in antibonding MOs and the relative importance of frontier orbitals. Just as an example, we show that orthodox antibonding orbitals can make a significant contribution of a bonding nature to a classical covalent bond or major contribution to DI(A,B) of an intramolecular and highly repulsive HH interaction.

FALDI-based criterion for and the origin of an electron density bridge with an associated (3,-1) critical point on Bader's molecular graph.

The total electron density (ED) along the λ2 -eigenvector is decomposed into contributions which either facilitate or hinder the presence of an electron density bridge (DB, often called an atomic interaction line or a bond path). Our FALDI-based approach explains a DB presence as a result of a dominating rate of change of facilitating factors relative to the rate of change of hindering factors; a novel and universal criterion for a DB presence is, thus, proposed. Importantly, facilitating factors show, in absolute terms, a concentration of ED in the internuclear region as commonly observed for most chemical bonds, whereas hindering factors show a depletion of ED in the internuclear region. We test our approach on four intramolecular interactions, namely (i) an attractive classical H-bond, (ii) a repulsive O⋅⋅⋅O interaction, (iii) an attractive Cl⋅⋅⋅Cl interaction, and (iv) an attractive CH⋅⋅⋅HC interaction. (Dis)appearance of a DB is (i) shown to be due to a "small" change in molecular environment and (ii) qualitatively and quantitatively linked with specific atoms and atom-pairs. The protocol described is equally applicable (a) to any internuclear region, (b) regardless of what kind of interaction (attractive/repulsive) atoms are involved in, (c) at any level of theory used to compute the molecular structure and corresponding wavefunction, and (d) equilibrium or nonequilibrium structures. Finally, we argue for a paradigm shift in the description of chemical interactions, from the ED perspective, in favor of a multicenter rather than diatomic approach in interpreting ED distributions in internuclear regions. © 2018 Wiley Periodicals, Inc.

Exact and exclusive electron localization indices within QTAIM atomic basins.

Novel measures of electron (de)localization within the Quantum Theory of Atoms in Molecules (QTAIM) atomic basins are presented which, unlike orthodox localization indices (LIs), are fully exclusive and can be easily visualized. This work shows that QTAIM-defined LIs describe a portion of interatomic delocalized electrons; hence, the chemical/physical interpretation of orthodox LIs is misleading. Using the recently introduced Fragment, Atomic, Localized, Delocalized, and Interatomic (FALDI) density decomposition technique we derive two novel sets of LIs and delocalization indices (DIs), by accounting for the overlap between localized and delocalized density functions. The FALDI-based LIs and DIs perfectly recover chemically expected core and bonded electron count. Usefulness of new (de)localization indices and their 3D representations were demonstrated on a number of examples, including formamide and benzene. We therefore expect that the scheme reported in this work will provide a valuable stepping stone between classical conceptual chemistry and quantum chemical topology. © 2018 Wiley Periodicals, Inc.

FALDI-based decomposition of an atomic interaction line leads to 3D representation of the multicenter nature of interactions.

Atomic interaction lines (AILs) and the QTAIM's molecular graphs provide a predominantly two-center viewpoint of interatomic interactions. While such a bicentric interpretation is sufficient for most covalent bonds, it fails to adequately describe both formal multicenter bonds as well as many non-covalent interactions with some multicenter character. We present an extension to our Fragment, Atomic, Localized, Delocalized and Interatomic (FALDI) electron density (ED) decomposition scheme, with which we can measure how any atom-pair's delocalized density concentrates, depletes or reduces the electron density in the vicinity of a bond critical point. We apply our method on five classical bonds/interactions, ranging from formal either two- or three-center bonds, a non-covalent interaction (an intramolecular hydrogen bond) to organometallic bonds with partial multicenter character. By use of 3D representation of specific atom-pairs contributions to the delocalized density we (i) fully recover previous notion of multicenter bonding in diborane and predominant bicentric character of a single covalent CC bond, (ii) reveal a multicenter character of an intramolecular H-bond and (iii) illustrate, relative to a Schrock carbene, a larger degree of multicenter MC interaction in a Fischer carbene (due to a presence of a heteroatom), whilst revealing the holistic nature of AILs from multicenter ED decomposition. © 2018 Wiley Periodicals, Inc.

Gold(I) Hydrides as Proton Acceptors in Dihydrogen Bond Formation.

Wavefunction and DFT calculations indicate that anionic dihydride complexes of AuI form strong to moderate directed Au-H⋅⋅⋅H bonds with one or two HF, H2 O and NH3 prototype proton donor molecules. The largely electrostatic interaction is influenced by relativistic effects which, however, do not increase the binding energy. Very weak Au⋅⋅⋅H associations-exhibiting a corresponding bond path-occur between neutral AuH and HF units, although ultimately F becomes the preferred donor atom in the most stable structure. Increasing the hydridicity of AuH by attachment of an electron donating NHC ligand effects Au-H⋅⋅⋅H bonding of moderate strength only with HF, whereas competing Au⋅⋅⋅H interactions dominate for H2 O and NH3 . Rare η2 coordinated and HX (X=F or OH) associated H2 complexes are produced during interaction with a single ion of stronger acidity, H2 F+ or H3 O+ . Theoretically, reaction of excess [AuH2 ]- as proton acceptor with H3 O+ or NH4+ in 3:1 or 4:1 ionic ratios, respectively, affords H⋅⋅⋅H bonded analogues of Eigen-type adducts. Outstanding analytical relationships between selected bonding parameters support the integrity of the results.

[Adherence to Long-term Follow-up in Paediatric Oncology--Results of a Monocentric Analysis]. / Nachsorgeadhärenz in der Pädiatrischen Onkologie - Ergebnisse einer monozentrischen Analyse.

BACKGROUND: Cured paediatric-oncology patients frequently present with health problems even years after treatment. Hence long-term follow-up (LTFU) is essential. This analysis tries to identify factors that influence regular LTFU attendance. STUDY POPULATION: Between 1991 and 2010, 2 153 children and adolescents were treated at Muenster University Department of Paediatric Hematology and Oncology (UKM). 1 708 patients with permanent residence in Germany and completed therapy have been included into this analysis. METHODS: Patients were reviewed for the duration and regularity of LTFU at UKM. Prospective analyses with postponed starting-points have been conducted as well as descriptive analyses to validate correlations. Prospective data were evaluated by Kaplan-Meier-Analyses, the analysis of multivariate correlations by Cox Proportional Hazard Model. RESULTS: 2 years after the end of therapy 83% of the patients were still in LTFU. After 5 and 10 years this percentage decreased to 67 and 42%. Patients diagnosed after the year 2000 and younger patients attended LTFU for a longer period (p<0,005). There were no significant gender differences. Statutory insured patients stayed longer in LTFU than private health insured (p<0,005). The multivariate examination showed only small differences between systemic diseases and solid tumours. The residential distance had no significant influence. CONCLUSIONS: Younger, more recently treated and statutory insured patients showed a significantly longer LTFU.

ENCCA WP17-WP7 consensus paper on teenagers and young adults (TYA) with bone sarcomas.

Teenagers and young adults (TYA) cancer contributes substantially to morbidity and mortality in a population with much to offer society. TYA place distinct challenges upon cancer care services, many reporting feeling marginalized and their needs not being met in adult or paediatric cancer services. Bone tumours such as osteosarcoma and Ewing sarcoma, because of their age at presentation and the complexity of their care, are where challenges in managing (TYA) with cancer have often been most readily apparent. Bone sarcomas may be managed by paediatric or medical oncologists, and require fastidious attention to protocol. A lack of recent improvement in survival in TYA with bone tumours may be linked to a lack of specialist care, poor concordance with therapy in some situations and TYA-specific pharmacology. Participation in clinical trials, particularly of young adults, is low, hindering progress. All these requirements may be best met by a concerted effort to create collaborative care between adult and paediatric experts in bone sarcoma, working together to meet TYA patients' needs.

Physical nature of interactions in Zn(II) complexes with 2,2'-bipyridyl: quantum theory of atoms in molecules (QTAIM), interacting quantum atoms (IQA), noncovalent interactions (NCI), and extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV) comparative studies.

In the present account factors determining the stability of ZnL, ZnL2, and ZnL3 complexes (L = bpy, 2,2'-bipyridyl) were characterized on the basis of various techniques: the quantum theory of atoms in molecules (QTAIM), energy decomposition schemes based on interacting quantum atoms (IQA), and extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV). Finally, the noncovalent interactions (NCI) index was also applied. All methods consistently indicated that the strength of the coordination bonds, Zn­O and Zn­N, decreases from ZnL to ZnL3. Importantly, it has been identified that the strength of secondary intramolecular heteropolar hydrogen bonding interactions, CH···O and CH···N, increases when going from ZnL to ZnL3. A similar trend appeared to be valid for the π-bonding as well as electrostatic stabilization. In addition to the above leading bonding contributions, all techniques suggested the existence of very subtle, but non-negligible additional stabilization from the CH···HC electronic exchange channel; these interactions are the weakest among all considered here. From IQA it was found that the local diatomic interaction energy, Eint(H,H), amounts at HF to −2.5, −2.7, and −2.9 kcal mol(­1) for ZnL, ZnL2, and ZnL3, respectively (−2.1 kcal mol(­1) for ZnL at MP2). NOCV-based deformation density channels showed that formation of CH--HC contacts in Zn complexes causes significant polarization of σ(C­H) bonds, which accordingly leads to charge accumulation in the CH···HC bay region. Charge depletion from σ(C­H) bonds was also reflected in the calculated spin­spin (1)J(C­H) coupling constants, which decrease from 177.06 Hz (ZnL) to 173.87 Hz (ZnL3). This last result supports our findings of an increase in the local electronic CH···HC stabilization from ZnL to ZnL3 found from QTAIM, IQA, and ETS-NOCV. Finally, this work unites for the first time the results from four methods that are widely used for description of chemical bonding.

Renal Ewing tumors.

BACKGROUND: Renal Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) is extremely rare. Clinical symptoms are nonspecific presenting abdominal pain, palpable mass, and hematuria. Owing to advanced technology demonstrating the ES-specific EWS/ETS translocation, this differential diagnosis has become feasible. PATIENTS AND METHODS: The German database of GPOH Ewing's sarcoma trials from 1980 to 2009 was searched for kidney as primary site. Twenty-four patients were identified and analyzed. The median time of observation was 3.71 years (range 0.27-8.75 years). Additionally, we carried out a Medline search for renal ES/PNET. RESULTS: The median age was 24.9 years (range 11-60 years). In 37.5%, patients presented with primary metastases. Tumor thrombi in the adjacent renal vessels occurred in 56.2%. In 90.9%, rearrangements of t(11;22) were found. All patients received a combined chemotherapy according to the EURO-E.W.I.N.G.99 protocol. In accordance, local control consisted predominantly of combined modality surgery and radiation (47%). At 3 years, overall survival (OS) was 0.80 (SE = 0.09), and event-free survival (EFS) 0.66 (SE = 0.11). CONCLUSIONS: ES/PNET should be considered in the differential diagnosis of renal tumors. Patients with renal ES/PNET respond to and benefit from conventional ES treatment according to ES study protocols. Therefore, an accurate diagnostic approach and a guideline-adapted therapy should be facilitated.

Ewing sarcoma of the hand or foot.

PURPOSE: Ewing Sarcoma (ES) of the hand or foot is a rare clinical condition. Due to the critical site, it is of major importance to choose an optimal procedure for local control in terms of outcome and function. Local therapeutic options for these patients range from: surgery (OP), surgery followed by radiotherapy (OP & RT), or radiotherapy (RT) alone. PATIENTS AND METHODS: Data from 80 patients with ES of the hand or foot were analyzed. All patients received chemotherapy according to the protocols of the Cooperative Ewing Sarcoma Study Group (CESS) from 1991 to 2009 (EICESS-92 and EURO-E.W.I.N.G.99). Local therapy consisted of: OP in 39%, OP & RT in 44%, and RT in 12%. In 5% of the patients no local therapy (noL) was performed. Primary endpoint of our study was the event-free-survival (EFS). RESULTS: The 3-year overall EFS was 62% (95%CI 0.50-0.72). Patients with localized disease had a significantly better outcome with an EFS of 77% (95%CI 0.63-0.86), compared to patients with primary disseminated disease with an EFS of 30% (95%CI 0.14-0.49; p<0.001). In comparing local treatment modalities, no significant difference was observed. The 3-year EFS for OP was 61% (95% CI 0.40-0.76), for OP & RT 66% (95%CI 0.47-0.79) and for RT only 70% (95%CI 0.32-0.89) (p=0.253). Patients who did not receive local treatment had an unfavourable prognosis (3-year EFS=0.25; 95%CI 0.01-0.67; p=0.024). A multivariate analysis which included local treatment modality and known prognosticators, showed that primary dissemination was the only significant prognostic factor.Ewing sarcoma of the hand or foot is associated with a favourable outcome. CONCLUSION: Our data analysed a limited group of patients and thus did not provide a clear indication for a preferred local treatment modality.

Evaluation of the prognostic meaning of C-reactive protein (CRP) in children and adolescents with classical Hodgkin's lymphoma (HL).

BACKGROUND: In adult cancer patients the negative predictive value of elevated CRP levels has been described for several malignancies. Only few studies have analyzed the prognostic role of CRP in children and adolescents with classical HL. In these studies elevated CRP levels correlate with the presence of classical risk factors and adverse outcome. PATIENTS AND METHODS: The prognostic role of CRP for patients with classical HL admitted to the GPOH-HD-2002 study was analyzed retrospectively. RESULTS: CRP levels were documented for 369 of 573 patients. Significant (p<0.05) increased median CRP levels were found in the presence of B-Symptoms (25.7 vs. 5.1 mg/l), extranodal involvement (21.5 vs. 7.5 mg/l), elevated erythrocyte sedimentation rate (ESR, 13.0 vs. 1.0 mg/l) and stage III/IV disease (15.5 vs. 5.3 mg/l). 83.9% of patients with elevated and 45.8% of patients with normal CRP had an ESR >30 mm/h. CONCLUSION: Elevated CRP levels were associated with classical risk factors of HL. CRP and ESR may reflect different biological processes. CRP was prognostic within early stage TG-1 patients treated with reduced treatment, but not within advanced stage TG-2+3.

Human leukocyte antigen distribution in German Caucasians with advanced Ewing's sarcoma.

BACKGROUND: Risk stratification criteria for patients with Ewing's sarcoma family of tumors (ESFT) are still limited. We hypothesized divergent human leukocyte antigen (HLA) patterns in ESFT patients and compared HLA-A, -B and -DR phenotype frequencies of patients with advanced ESFT with those of healthy controls. PATIENTS: HLA types of all German Caucasian patients with advanced ESFT and available HLA-A, -B and -DR data registered in the European Group for Blood and Marrow Transplantation, Paediatric Registry for Stem Cell Transplantation and the MetaEICESS data bases (study group, n=30) were retrospectively compared with HLA types of healthy German stem cell donors (control group, n=8 862 for single HLA frequencies and n=8 839 for allele combinations). Study group patients had been immuno-typed due to eligibility for allogeneic stem cell transplantation for high risk of treatment failure, and thus constituted a selected subgroup of ESFT patients. RESULTS: After Bonferroni correction for multiple testing (PC), phenotype frequencies of HLA-A24 remained significantly higher in the study group compared to controls (PC<0.05). Furthermore, several HLA combinations were significantly more frequent in the study group compared to controls (all PC<0.05). CONCLUSION: We report an increased incidence of circumscribed HLA patterns in German Caucasians with advanced ESFT. The possible clinical significance of this observation has to be re-assessed in prospective trials comprising larger ESFT patient numbers of all risk groups.

High STEAP1 expression is associated with improved outcome of Ewing's sarcoma patients.

BACKGROUND: Ewing's sarcoma (ES) is the second most common bone or soft-tissue sarcoma in childhood and adolescence and features a high propensity to metastasize. The six-transmembrane epithelial antigen of the prostate 1 (STEAP1) is a membrane-bound mesenchymal stem cell marker highly expressed in ES. Here, we investigated the role of STEAP1 as an immunohistological marker for outcome prediction in patients with ES. PATIENTS AND METHODS: Membranous STEAP1 immunoreactivity was analyzed using immunohistochemistry in 114 primary pre-chemotherapy ES of patients diagnosed from 1983 to 2010 and compared with clinical parameters and patient outcome. Median follow-up was 3.85 years (range 0.43-17.51). RESULTS: A total of 62.3% of the ES samples displayed detectable STEAP1 expression with predominant localization of the protein at the plasma membrane. High membranous STEAP1 immunoreactivity was found in 53.5%, which correlated with better overall survival (P=0.021). Accordingly, no or low membranous STEAP1 expression was identified as an independent risk factor in multivariate analysis (hazard ratio 2.65, P=0.036). CONCLUSION: High membranous STEAP1 expression predicts improved outcome and may help to define a specific subgroup of ES patients, who might benefit from adapted therapy regimens.