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All sources NASA NTRS DOE OSTI

DOE OSTI2024

Development and crystal structures of a potent second-generation dual degrader of BCL-2 and BCL-xL

Overexpression of BCL-xL and BCL-2 play key roles in tumorigenesis and cancer drug resistance. Advances in PROTAC technology facilitated recent development of the first BCL-xL/BCL-2 dual degrader, 753b, a VHL-based degrader with improved potency and reduced toxicity compared to previous small molecule inhibitors. Here, we determine crystal structures of VHL/753b/BCL-xL and VHL/753b/BCL-2 ternary complexes. The two ternary complexes exhibit markedly different architectures that are accompanied by distinct networks of interactions at the VHL/753b-linker/target interfaces. The importance of these interfacial contacts is validated via functional analysis and informed subsequent rational and structure-guided design focused on the 753b linker and BCL-2/BCL-xL warhead. This results in the design of a degrader, WH244, with enhanced potency to degrade BCL-xL/BCL-2 in cells. Using biophysical assays followed by in cell activities, we are able to explain the enhanced target degradation of BCL-xL/BCL-2 in cells. Most PROTACs are empirically designed and lack structural studies, making it challenging to understand their modes of action and specificity. Our work presents a streamlined approach that combines rational design and structure-based insights backed with cell-based studies to develop effective PROTAC-based cancer therapeutics.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Corrigendum to: The human Bcl-2 family member Bcl-rambo and voltage-dependent anion channels manifest a genetic interaction in Drosophila and cooperatively promote the activation of effector caspases in human cultured cells

No abstract prepared.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2025

First-Principles Dissociation Pathways of BCl 3 on the Si(100)-2 × 1 Surface

BCl 3 is a promising acceptor precursor for atomic-precision δ-doping of silicon, as it has been observed to rapidly dissociate into boron doped into the silicon surface and surface chlorine, which can be removed upon annealing. The chemical pathway and the resulting kinetics, through which BCl 3 adsorbs and dissociates on silicon, however, have only been partially explained. Here, in this work, we use density functional theory to expand the dissociation reactions of BCl 3 to include reactions that take place across multiple silicon dimer rows and reactions which end in a bare B atom either at the surface, substituted for a surface silicon, or in a subsurface position. We further simulate the resulting scanning tunneling microscopy images for each of these BCl x dissociation fragments, demonstrating that they often display distinct features that may allow for relatively confident experimental identification. Finally, we input the full dissociation pathway for BCl 3 into a kinetic Monte Carlo model, which simulates realistic reaction pathways as a function of environmental conditions, such as the pressure and temperature of dosing. We find that BCl 2 is broadly dominant at low temperatures, while high temperatures and ample space on the silicon surface for dissociation encourage the formation of bridging BCl fragments and B substitutions on the surface. This work provides the chemical mechanisms for understanding atomic-precision doping of Si with B, enabling a number of relevant quantum applications, such as bipolar nanoelectronics, acceptor-based qubits, and superconducting Si.

Campbell, Quinn T. [Sandia National Laboratories (↗

NASA NTRS2002

Gene conversion is strongly induced in human cells by double-strand breaks and is modulated by the expression of BCL-x(L)

Homology-directed repair (HDR) of DNA double-strand breaks (DSBs) contributes to the maintenance of genomic stability in rodent cells, and it has been assumed that HDR is of similar importance in DSB repair in human cells. However, some outcomes of homologous recombination can be deleterious, suggesting that factors exist to regulate HDR. We demonstrated previously that overexpression of BCL-2 or BCL-x(L) enhanced the frequency of X-ray-induced TK1 mutations, including loss of heterozygosity events presumed to arise by mitotic recombination. The present study was designed to test whether HDR is a prominent DSB repair pathway in human cells and to determine whether ectopic expression of BCL-x(L) affects HDR. Using TK6-neo cells, we find that a single DSB in an integrated HDR reporter stimulates gene conversion 40-50-fold, demonstrating efficient DSB repair by gene conversion in human cells. Significantly, DSB-induced gene conversion events are 3-4-fold more frequent in TK6 cells that stably overexpress the antiapoptotic protein BCL-X(L). Thus, HDR plays an important role in maintaining genomic integrity in human cells, and ectopic expression of BCL-x(L) enhances HDR of DSBs. This is the first study to highlight a function for BCL-x(L) in modulating DSB repair in human cells.

NASA Discipline Radiation Health↗

DOE OSTI2020

Materials Data on Ag(BCl)6 by Materials Project

Ag(BCl)6 is alpha-like structured and crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of eight Ag(BCl)6 clusters. Ag is bonded in a 6-coordinate geometry to six Cl atoms. There are three shorter (2.87 Å) and three longer (2.88 Å) Ag–Cl bond lengths. There are two inequivalent B sites. In the first B site, B is bonded in a single-bond geometry to one Cl atom. The B–Cl bond length is 1.79 Å. In the second B site, B is bonded in a single-bond geometry to one Cl atom. The B–Cl bond length is 1.80 Å. There are two inequivalent Cl sites. In the first Cl site, Cl is bonded in a distorted single-bond geometry to one Ag and one B atom. In the second Cl site, Cl is bonded in a distorted water-like geometry to one Ag and one B atom.

36 MATERIALS SCIENCE↗

NASA NTRS1980

New technologies for solar energy silicon - Cost analysis of BCL process

New technologies for producing polysilicon are being developed to provide lower cost material for solar cells which convert sunlight into electricity. This article presents results for the BCL Process, which produces the solar-cell silicon by reduction of silicon tetrachloride with zinc vapor. Cost, sensitivity, and profitability analysis results are presented based on a preliminary process design of a plant to produce 1000 metric tons/year of silicon by the BCL Process. Profitability analysis indicates a sales price of $12.1-19.4 per kg of silicon (1980 dollars) at a 0-25 per cent DCF rate of return on investment after taxes. These results indicate good potential for meeting the goal of providing lower cost material for silicon solar cells.

Yaws, C. L.↗

DOE OSTI2020

Materials Data on BCl by Materials Project

BCl crystallizes in the orthorhombic P2_12_12_1 space group. The structure is zero-dimensional and consists of thirty-two chloroborane molecules. B is bonded in a distorted single-bond geometry to one Cl atom. The B–Cl bond length is 1.73 Å. Cl is bonded in a single-bond geometry to one B atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BCl by Materials Project

BCl is Cubane-like structured and crystallizes in the tetragonal P4_2/nmc space group. The structure is zero-dimensional and consists of eight chloroborane molecules. B is bonded in a single-bond geometry to one Cl atom. The B–Cl bond length is 1.73 Å. Cl is bonded in a single-bond geometry to one B atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Pr8(BCl)7 by Materials Project

Pr8(BCl)7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are eight inequivalent Pr+3.50+ sites. In the first Pr+3.50+ site, Pr+3.50+ is bonded in a 7-coordinate geometry to five B3- and four Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.61–3.01 Å. There are a spread of Pr–Cl bond distances ranging from 2.92–3.26 Å. In the second Pr+3.50+ site, Pr+3.50+ is bonded in a 7-coordinate geometry to five B3- and four Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.62–3.00 Å. There are a spread of Pr–Cl bond distances ranging from 2.91–3.26 Å. In the third Pr+3.50+ site, Pr+3.50+ is bonded to one B3- and five Cl1- atoms to form distorted PrBCl5 pentagonal pyramids that share corners with two BPr4B3 pentagonal bipyramids and an edgeedge with one PrBCl5 pentagonal pyramid. The Pr–B bond length is 2.66 Å. There are a spread of Pr–Cl bond distances ranging from 2.88–3.03 Å. In the fourth Pr+3.50+ site, Pr+3.50+ is bonded in a 6-coordinate geometry to one B3- and five Cl1- atoms. The Pr–B bond length is 2.49 Å. There are a spread of Pr–Cl bond distances ranging from 2.88–3.03 Å. In the fifth Pr+3.50+ site, Pr+3.50+ is bonded in a 9-coordinate geometry to five B3- and four Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.63–2.94 Å. There are a spread of Pr–Cl bond distances ranging from 3.13–3.28 Å. In the sixth Pr+3.50+ site, Pr+3.50+ is bonded in a 9-coordinate geometry to six B3- and three Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.71–2.74 Å. There are one shorter (2.97 Å) and two longer (3.06 Å) Pr–Cl bond lengths. In the seventh Pr+3.50+ site, Pr+3.50+ is bonded in a 7-coordinate geometry to eight B3- and three Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.70–3.06 Å. There are one shorter (2.96 Å) and two longer (3.15 Å) Pr–Cl bond lengths. In the eighth Pr+3.50+ site, Pr+3.50+ is bonded in a 9-coordinate geometry to five B3- and four Cl1- atoms. There are a spread of Pr–B bond distances ranging from 2.63–2.93 Å. There are a spread of Pr–Cl bond distances ranging from 3.13–3.35 Å. There are seven inequivalent B3- sites. In the first B3- site, B3- is bonded in a 5-coordinate geometry to six Pr+3.50+ and three B3- atoms. There are a spread of B–B bond distances ranging from 1.68–1.96 Å. In the second B3- site, B3- is bonded in a 9-coordinate geometry to six Pr+3.50+ and three B3- atoms. There is one shorter (1.68 Å) and one longer (1.90 Å) B–B bond length. In the third B3- site, B3- is bonded to four Pr+3.50+ and three B3- atoms to form distorted BPr4B3 pentagonal bipyramids that share a cornercorner with one PrBCl5 pentagonal pyramid, an edgeedge with one BPr5B octahedra, edges with two BPr4B3 pentagonal bipyramids, and a faceface with one BPr4B3 pentagonal bipyramid. There is one shorter (1.64 Å) and one longer (1.74 Å) B–B bond length. In the fourth B3- site, B3- is bonded in a 7-coordinate geometry to five Pr+3.50+ and two B3- atoms. The B–B bond length is 1.74 Å. In the fifth B3- site, B3- is bonded to five Pr+3.50+ and one B3- atom to form edge-sharing BPr5B octahedra. The B–B bond length is 1.74 Å. In the sixth B3- site, B3- is bonded in a 3-coordinate geometry to six Pr+3.50+ and three B3- atoms. In the seventh B3- site, B3- is bonded to four Pr+3.50+ and three B3- atoms to form distorted BPr4B3 pentagonal bipyramids that share a cornercorner with one PrBCl5 pentagonal pyramid, an edgeedge with one BPr5B octahedra, edges with two BPr4B3 pentagonal bipyramids, and a faceface with one BPr4B3 pentagonal bipyramid. There are eight inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Pr+3.50+ atoms. In the second Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Pr+3.50+ atoms. In the third Cl1- site, Cl1- is bonded in a 3-coordinate geometry to three Pr+3.50+ atoms. In the fourth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Pr+3.50+ atoms. In the fifth Cl1- site, Cl1- is bonded in a 6-coordinate geometry to six Pr+3.50+ atoms. In the sixth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Pr+3.50+ atoms. In the seventh Cl1- site, Cl1- is bonded in a 3-coordinate geometry to three Pr+3.50+ atoms. In the eighth Cl1- site, Cl1- is bonded in a 6-coordinate geometry to six Pr+3.50+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BCl by Materials Project

BCl crystallizes in the cubic Pa-3 space group. The structure is zero-dimensional and consists of forty-eight chloroborane molecules. B is bonded in a single-bond geometry to one Cl atom. The B–Cl bond length is 1.75 Å. Cl is bonded in a single-bond geometry to one B atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Reaction of BCl 3 with H- and Cl-terminated Si(100) as a pathway for selective, monolayer doping through wet chemistry

The reaction of boron trichloride with the H and Cl-terminated Si(100) surfaces was investigated to understand the interaction of this molecule with the surface for designing wet-chemistry based silicon surface doping processes using a carbon- and oxygen-free precursor. The process was followed with X-ray photoelectron spectroscopy (XPS). Within the reaction conditions investigated, the reaction is highly effective on Cl-Si(100) for temperatures below 70°C, at which point both surfaces react with BCl$_3$. The XPS investigation followed the formation of a B 1s peak at 193.5 eV corresponding to (B-O)$_x$ species. Even the briefest exposure to ambient conditions lead to hydroxylation of surface borochloride species. However, the Si 2p signature at 102 eV allowed for a confirmation of the formation of a direct Si-B bond. Density functional theory was utilized to supplement the analysis and identify possible major surface species resulting from these reactions. This work provides a new pathway to obtain a functionalized silicon surface with a direct Si-B bond that can potentially be exploited as a means of selective, ultra-shallow, and supersaturated doping.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Materials Data on BCl(OF2)2 by Materials Project

BF4ClO2 crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four hypochlorous acid;hydrate molecules and four BF4 clusters. In each BF4 cluster, B is bonded in a tetrahedral geometry to four F atoms. There are a spread of B–F bond distances ranging from 1.39–1.45 Å. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one B atom. In the second F site, F is bonded in a single-bond geometry to one B atom. In the third F site, F is bonded in a single-bond geometry to one B atom. In the fourth F site, F is bonded in a single-bond geometry to one B atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BCl(OF2)2 by Materials Project

BF4ClO2 crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of four hypochlorous acid;hydrate molecules and four BF4 clusters. In each BF4 cluster, B is bonded in a tetrahedral geometry to four F atoms. There are a spread of B–F bond distances ranging from 1.40–1.47 Å. There are four inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one B atom. In the second F site, F is bonded in a single-bond geometry to one B atom. In the third F site, F is bonded in a single-bond geometry to one B atom. In the fourth F site, F is bonded in a single-bond geometry to one B atom.

36 MATERIALS SCIENCE↗

DOE OSTI2021