A University-Based Social Services Parent-Training Model: A Telehealth Adaptation During the COVID-19 Pandemic.

With the COVID-19 pandemic resulting in social-distancing recommendations, many service providers find themselves altering the way they must provide medically necessary therapy. Even with the advent of more advanced telehealth technologies, the implementation of behavioral programming falls mainly on the caregivers of the clients that are served. This crisis brings to light ethical dilemmas and upends the current ways many programs may have been implemented across the world. As a result, a reevaluation of how these services are delivered is in order. This article reviews how a university-based, state-funded service delivery program (USSDP) provided essential and necessary services during the COVID-19 pandemic. Specifically, the purpose of this article is to describe how the USSDP quickly adopted a telehealth care model in a program that previously had not delivered services in this modality. Ethical, contextual, and competency-based factors are reviewed in the context of this organization, followed by a dialogue on broader generalization suggestions utilizing an active support model of care within telehealth restrictions.

Behavior description effect on accuracy and reliability.

The clinical and scientific efficacy of behavioral analysis is dependent upon interveners' accurate and reliable detection and measurement of target behaviors. This study compared the accuracy and reliability of observers' detection and recording of a designated target behavior when different forms of a target behavior description were used. Using an intra-subject design, undergraduate college students were asked to count the number of target behaviors depicted on a videotape under each of two conditions. Conditions differed only to the extent that each contained a different description of the target behavior. Results showed that participants' detection and recording of the target behavior was more accurate and reliable when the target behavior description used a verb (in the present tense, active voice) depicting an action with an observable and discrete beginning and end and omitted modifiers requiring observers to make subjective or relative judgments. Analysis of the data using methods developed by Signal Detection Theory demonstrated the potential utility of this approach for studying observer detection of target behaviors.

Structure of Staphylococcus aureus 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase.

5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) catalyzes the irreversible cleavage of the glycosidic bond in 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH) and plays a key role in four metabolic processes: biological methylation, polyamine biosynthesis, methionine recycling and bacterial quorum sensing. The absence of the nucleosidase in mammalian species has implicated this enzyme as a target for antimicrobial drug design. MTAN from the pathogenic bacterium Staphylococcus aureus (SaMTAN) has been kinetically characterized and its structure has been determined in complex with the transition-state analogue formycin A (FMA) at 1.7 A resolution. A comparison of the SaMTAN-FMA complex with available Escherichia coli MTAN structures shows strong conservation of the overall structure and in particular of the active site. The presence of an extra water molecule, which forms a hydrogen bond to the O4' atom of formycin A in the active site of SaMTAN, produces electron withdrawal from the ribosyl group and may explain the lower catalytic efficiency that SaMTAN exhibits when metabolizing MTA and SAH relative to the E. coli enzyme. The implications of this structure for broad-based antibiotic design are discussed.

ADP-2Ho as a phasing tool for nucleotide-containing proteins.

Trivalent holmium ions were shown to isomorphously replace magnesium ions to form an ADP-2Ho complex in the nucleotide-binding domain of Bacillus subtilis 5-methylthioribose (MTR) kinase. This nucleotide-holmium complex provided sufficient phasing power to allow SAD and SIRAS phasing of this previously unknown structure using the L(III) absorption edge of holmium. The structure of ADP-2Ho reveals that the two Ho ions are approximately 4 A apart and are likely to share their ligands: the phosphoryl O atoms of ADP and a water molecule. The structure determination of MTR kinase using data collected using Cu Kalpha X-radiation was also attempted. Although the heavy-atom substructure determination was successful, interpretation of the map was more challenging. The isomorphous substitution of holmium for magnesium in the MTR kinase-nucleotide complex suggests that this could be a useful phasing tool for other metal-dependent nucleotide-containing proteins.

Substructure determination in multiwavelength anomalous diffraction, single anomalous diffraction, and single isomorphous replacement with anomalous scattering data using Shake-and-Bake.

A general method for selenium and sulfur substructure determination using the Shake-and-Bake (SnB) algorithm as implemented in SnB in conjunction with anomalous difference E magnitudes is presented. The protocol can be used for Se-Met multiwavelength anomalous diffraction, seleneomethionine single anomalous diffraction (SAD), S-SAD and S/Se-single isomorphous replacement with anomalous scattering data and with minor modifications for other heavy atom derivatives, such as the location of halides.

The structure of T6 bovine insulin.

Porcine insulin differs in sequence from bovine insulin at residues A8 (Thr in porcine-->Ala in bovine) and A10 (Ile in porcine-->Val in bovine). The structure of T6 hexameric bovine insulin has been determined to 2.25 A resolution at room temperature and refined to a residual of 0.162. The structure of the independent dimer is nearly identical to the T6 porcine insulin dimer: the mean displacement of all backbone atoms is 0.16 A, with the largest displacements occurring at AlaB30. Each of two independent zinc ions is octahedrally coordinated by three HisB10 side chains and three water molecules. As has been observed in both human and porcine insulin, the GluB13 side chains are directed towards the center of the hexamer, where a short contact of 2.57 A occurs between two independent carboxyl O atoms, again suggesting the presence of a centered hydrogen bond. No significant displacements of backbone atoms or changes in conformation are observed at A8 or A10. Since there are no interhexamer hydrogen-bonded contacts involving A8 in either porcine or bovine insulin, the change in the identity of this residue appears to have little or no effect upon the packing of the hexamers in the unit cell. In contrast, the side chains of the three A10 residues in one trimer make van der Waals contacts with the A10 side chains in a translationally related hexamer. As a consequence of the loss of the C(delta1) atom from the isoleucine residue in porcine insulin to produce valine in bovine insulin, there is a 0.36 A decrease in the distance between independent pairs of C(beta) atoms and a 0.24 A decrease in the c dimension of the unit cell. Thus, the net effect of the change in sequence at A10 is to strengthen the stabilizing hydrophobic interactions between hexamers.

Structural snapshots of MTA/AdoHcy nucleosidase along the reaction coordinate provide insights into enzyme and nucleoside flexibility during catalysis.

MTA/AdoHcy nucleosidase (MTAN) irreversibly hydrolyzes the N9-C1' bond in the nucleosides, 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (AdoHcy) to form adenine and the corresponding thioribose. MTAN plays a vital role in metabolic pathways involving methionine recycling, biological methylation, polyamine biosynthesis, and quorum sensing. Crystal structures of a wild-type (WT) MTAN complexed with glycerol, and mutant-enzyme and mutant-product complexes have been determined at 2.0A, 2.0A, and 2.1A resolution, respectively. The WT MTAN-glycerol structure provides a purine-free model and in combination with the previously solved thioribose-free MTAN-ADE structure, we now have separate apo structures for both MTAN binding subsites. The purine and thioribose-free states reveal an extensive enzyme-immobilized water network in their respective binding subsites. The Asp197Asn MTAN-MTA and Glu12Gln MTAN-MTR.ADE structures are the first enzyme-substrate and enzyme-product complexes reported for MTAN, respectively. These structures provide representative snapshots along the reaction coordinate and allow insight into the conformational changes of the enzyme and the nucleoside substrate. A "catalytic movie" detailing substrate binding, catalysis, and product release is presented.

Structural studies of duck delta2 crystallin mutants provide insight into the role of Thr161 and the 280s loop in catalysis.

Delta crystallin, a taxon-specific crystallin present in avian eye lenses, is homologous to the urea cycle enzyme ASL (argininosuccinate lyase). Although there are two delta crystallin isoforms in duck lenses, ddeltac1 (duck delta1 crystallin) and ddeltac2 (duck delta2 crystallin), only ddeltac2 is catalytically active. Previous structural studies have suggested that residues Ser283 and His162 in the multi-subunit active site of ddeltac2/ASL are the putative catalytic acid/base, while the highly conserved, positively charged Lys289 is thought to help stabilize the carbanion intermediate. The strict conservation of a small hydroxy-containing residue (Thr or Ser) at position 161 adjacent to the putative catalytic base, as well as its proximity to the substrate in the S283A ddeltac2 enzyme-substrate complex, prompted us to investigate further the role this residue. Structures of the active T161S and inactive T161D ddeltac2 mutants, as well as T161D complexed with argininosuccinate, have been determined to 2.0 A resolution. The structures suggest that a hydroxy group is required at position 161 to help correctly position the side chain of Lys289 and the fumarate moiety of the substrate. Threonine is probably favoured over serine, because the interaction of its methyl group with Leu206 would restrict its conformational flexibility. Residues larger than Thr or Ser interfere with substrate binding, supporting previous suggestions that correct positioning of the substrate's fumarate moiety is essential for catalysis to occur. The presence of the 280s loop (i.e. a loop formed by residues 270-290) in the 'open' conformation suggests that loop closure, thought to be essential for sequestration of the substrate, may be triggered by the formation of the carbanion or aci-carboxylate intermediates, whose charge distribution more closely mimics that of the sulphate ion found in the active-site region of the inactive ddeltac1. The 280s loop in ddeltac1 is in the closed conformation.

Lessons from an aged, dried crystal of T(6) human insulin.

The structure of the T(6) hexameric form of human insulin has been determined at both room temperature and 100 K from a single air-dried crystal. At 100 K, the space group is R3 and the asymmetric unit consists of a dimer, as has been observed previously in hydrated structures. At room temperature, the space group is P1 and the unit cell contains a quasi-threefold-symmetric hexamer. In the absence of stabilizing water interactions, the N-termini of all six A chains in the room-temperature structure appear to have undergone partial unfolding, but the N-termini of these chains are well ordered in the 100 K structure. Other differences between the room-temperature and 100 K structures involve the coordination around the zinc ions. At 100 K, both zinc ions clearly exhibit dual coordination: zinc is octahedrally coordinated in one half of the zinc sites but tetrahedrally coordinated in the other half; at room temperature, the electron densities suggest tetrahedral coordination but the bond distances to the fourth ligands are longer than expected. Contrary to what has been observed to date in all other T(6) insulin structures, there are no contacts between pairs of GluB13 residues, either at room temperature or at 100 K, that would suggest the presence of a hydrogen bond. At room temperature, three of the six independent GluB13 side chains are disordered; at 100 K, both independent side chains are disordered. The disorder in the GluB13 side chains and the lack of contacts between carboxylate groups suggests that as a result of disruption of the hydration structure in the central core of the hexamer, all six B13 carboxylates bear a negative charge. This in turn suggests that in the hydrated structures the well ordered water structure in the central core is involved in stabilizing the B13 side-chain conformations and modulating charge repulsions among the six B13 glutamates if they are not protonated, or that, as is considered more likely, the water structure plays an important role in modulating the pK(a) values of the B13 glutamates, resulting in protonation and hydrogen-bond formation.

The structure of T6 human insulin at 1.0 A resolution.

The structure of T(6) human insulin has been determined at 120 K at a resolution of 1.0 A and refined to a residual of 0.183. As a result of cryofreezing, the first four residues of the B chain in one of the two crystallographically independent AB monomers in the hexameric [Zn(1/3)(AB)(2)Zn(1/3)](3) complex undergo a conformational shift that displaces the C(alpha) atom of PheB1 by 7.86 A relative to the room-temperature structure. A least-squares superposition of all backbone atoms of the room-temperature and low-temperature structures yielded a mean displacement of 0.422 A. Omitting the first four residues of the B chain reduced the mean displacement to 0.272 A. At 120 K, nine residues were found to exhibit two discrete side-chain conformations, but only two of these residues are in common with the seven residues found to have disordered side chains in the room-temperature structure. As a result of freezing, the disorder observed at room temperature in both ArgB22 side chains is eliminated. The close contact between pairs of O( epsilon 2) atoms in GluB13 observed at room temperature is maintained at cryotemperature and suggests that a carboxylate-carboxylic acid centered hydrogen bond exists [-C(=O)-O.H.O-C(=O)-] such that the H atom is equally shared between the two partially charged O atoms.

S-SAD, Se-SAD and S/Se-SIRAS using Cu Kalpha radiation: why wait for synchrotron time?

The structure of Escherichia coli argininosuccinate synthetase (EAS) has been determined using S-SAD, Se-SAD and S/Se-SIRAS data measured with Cu Kalpha radiation. EAS contains 16 methionines and three cysteines in 455 amino acids. At a wavelength of 1.54 A (Cu Kalpha), the native (S-Met) and derivative (Se-Met) proteins yield anomalous signals of approximately 0.86 and 1.6%, respectively. Highly redundant data were measured to 2.0 A from native and derivative EAS crystals. All three structure determinations were carried out in a highly automated manner using SnB and SOLVE/RESOLVE. Despite the minute Bijvoet differences at 1.54 A, the signal was sufficient to determine the heavy-atom substructure and produce high-quality electron-density maps in all three cases. These maps were readily interpretable by the RESOLVE automated building algorithm, which modeled greater than 75% of all three structures. The success of these methods has profound implications for crystallographers experiencing difficulty with heavy-atom incorporation or with limited access to a synchrotron source.