A process evaluation of the NIDUS-Professional dementia training intervention for UK homecare workers.

INTRODUCTION: This process evaluation was conducted in parallel to the randomised controlled feasibility trial of NIDUS-Professional, a manualised remote dementia training intervention for homecare workers (HCWs), delivered alongside an individualised intervention for clients living with dementia and their family carers (NIDUS-Family). The process evaluation reports on: (i) intervention reach, dose and fidelity; (ii) contexts influencing agency engagement and (iii) alignment of findings with theoretical assumptions about how the intervention might produce change. METHODS: We report proportions of eligible HCWs receiving any intervention (reach), number of sessions attended (dose; attending ≥4/6 main sessions was predefined as adhering), intervention fidelity and adherence of clients and carers to NIDUS-Family (attending all 6-8 planned sessions). We interviewed HCWs, managers, family carers and facilitators. We integrated and thematically analysed, at the homecare agency level, qualitative interview and intervention recording data. RESULTS: 32/141 (23%) of eligible HCWs and 7/42 (17%) of family carers received any intervention; most who did adhered to the intervention (89% and 71%). Intervention fidelity was high. We analysed interviews with 20/44 HCWs, 3/4 managers and 3/7 family carers, as well as intervention recordings involving 32/44 HCWs. All agencies reported structural challenges in supporting intervention delivery. Agencies with greater management buy-in had higher dose and reach. HCWs valued NIDUS-Professional for enabling group reflection and peer support, providing practical, actionable care strategies and increasing their confidence as practitioners. CONCLUSION: NIDUS-Professional was valued by HCWs. Agency management, culture and priorities were key barriers to implementation; we discuss how to address these in a future trial.

A Web-Based Self-management App for Living Well With Dementia: User-Centered Development Study.

BACKGROUND: Self-management, autonomy, and quality of life are key constructs in enabling people to live well with dementia. This population often becomes isolated following diagnosis, but it is important for them to feel encouraged to maintain their daily activities and stay socially active. Promoting Independence in Dementia (PRIDE) fosters social inclusion and greater dementia self-management through an interactive handbook. OBJECTIVE: This study aimed to develop a paper-based PRIDE manual on a web-based platform. METHODS: Two overarching stages were used to create the web-based version of PRIDE. The first was Preliminary Development, which encompassed tendering, preliminary development work, consultations, beta version of the website, user testing and consultation on beta version, and production of the final web-based prototype. The second stage was Development of the Final PRIDE App, which included 2 sprints and further user testing. RESULTS: Through a lengthy development process, modifications were made to app areas such as the log-in process, content layout, and aesthetic appearance. Feedback from the target population was incorporated into the process to achieve a dementia-friendly product. The finished PRIDE app has defined areas for reading dementia-related topics, creating activity plans, and logging these completed activities. CONCLUSIONS: The PRIDE app has evolved from its initial prototype into a more dementia-friendly and usable program that is suitable for further testing. The finished version will be tested in a reach, effectiveness, adoption, implementation, and maintenance study, with its potential reach, effectiveness, and adoption explored. Feedback gathered during the reach, effectiveness, adoption, implementation, and maintenance study will lead to any further developments in the app to increase its applicability to the target audience and usability.

Feasibility and acceptability of NIDUS-Professional, a training and support intervention for homecare workers caring for clients living with dementia: a cluster-randomised feasibility trial protocol.

INTRODUCTION: Most people living with dementia want to remain living in their own homes, and are supported to do so by family carers and homecare workers. There are concerns that homecare is often unable to meet the needs of this client group, with limited evidence regarding effective interventions to improve it for people living with dementia. We have developed a training and support programme for homecare workers (NIDUS-Professional) to be delivered alongside support sessions for people living with dementia and their family carers (NIDUS-Family). We aim to assess (1) its acceptability among homecare workers and employing agencies, and (2) the feasibility of homecare workers, people living with dementia and their family carers completing the outcomes of intervention in a future randomised controlled trial. METHODS AND ANALYSIS: This is a cluster-randomised (2:1) single-blind, multisite feasibility trial. We aim to recruit 60-90 homecare workers, 30-60 clients living with dementia and their family carers through 6-9 English homecare agencies. In the intervention arm, homecare staff will be offered six group sessions on video call over three months, followed by monthly group sessions over the subsequent three-month period. Outcome measures will be collected at baseline and at six months. ETHICS AND DISSEMINATION: The study received ethical approval on 7 January 2020 from the Camden & King's Cross Research Ethics Committee. Study reference: 19/LO/1667. Findings will be disseminated through a peer-reviewed journal, conference presentation and blog to research and clinical audiences; we will attend forums to present findings to participating homecare agencies and their clients. TRIAL REGISTRATION NUMBER: ISRCTN15757555.

Time to reflect is a rare and valued opportunity; a pilot of the NIDUS-professional dementia training intervention for homecare workers during the Covid-19 pandemic.

Most people living with dementia want to continue living in their own home for as long as possible and many rely on support from homecare services to do so. There are concerns that homecare often fails to meet the needs of clients with dementia, but there is limited evidence regarding effective interventions to improve its delivery for this client group. We aimed to assess whether a co-designed, 6-session dementia training intervention for homecare workers (NIDUS-professional) was acceptable and feasible. Facilitated training sessions were delivered over 3 months, followed by 3, monthly implementation meetings to embed changes in practice. Two trained and supervised facilitators without clinical qualifications delivered the intervention via group video-calls during Oct 2020-March 2021 to a group of seven homecare workers from one agency in England. Participants provided qualitative feedback 3- and 6-months post intervention. Qualitative interview data and facilitator notes were integrated in a thematic analysis. Adherence to the intervention and fidelity of delivery were high, indicating that it was acceptable and feasible to deliver in practice. Thirty of a possible 42 (71.4%) group sessions were attended. In our thematic analysis we report one over-arching theme: 'Having time and space to reflect is a rare opportunity'. Within this we identified four subthemes (Having time to reflect is a rare opportunity; Reflecting with peers enhances learning; Reflection and perspective taking can improve care; Recognising skills and building confidence) through which we explored how participants valued the intervention to discuss their work and learn new skills. Attendance was lower for the implementation sessions, perhaps reflecting participants' lack of clarity about their purpose. We used our findings to consider how we can maintain positive impacts of the manualised sessions, so that these are translated into tangible, scalable benefits for people living with dementia and the homecare workforce. A randomised feasibility trial is underway.

Co-designing complex interventions with people living with dementia and their supporters.

BACKGROUND AND OBJECTIVES: We engaged people living with dementia, family carers and health and social care professionals in co-designing two dementia care interventions: for family carers and people living with dementia (New Interventions for Independence in Dementia Study (NIDUS)-family and home-care workers (NIDUS-professional training programme). RESEARCH DESIGN AND METHODS: Over October 2019-March 2020, we invited public and patient (PPI) and professional members of our NIDUS co-design groups to complete the PPI Engagement Evaluation Tool (designed to assess engagement activities), and non-professional PPI members to participate in qualitative telephone interviews. We thematically analysed and integrated mixed-methods findings. RESULTS: Most (15/20; 75%) of the PPI members approached participated. We identified four themes: (1) Creating the right atmosphere: participants found group meetings positive and enabling, though one health professional was unsure how to position themselves within them; (2) Participants influencing the outcome: while most members felt that they had some influence, for one carer consultation seemed too late to influence; (3) Having the right information: several carers wanted greater clarity and more regular updates from researchers; (4) Unique challenges for people living with dementia: memory problems presented challenges in engaging with substantial information, and within a large group. DISCUSSION AND IMPLICATIONS: We reflect on the importance of providing accessible, regular updates, managing power imbalances between co-design group members with lived and professional experiences; and ensuring needs and voices of people living with dementia are prioritised. We encourage future studies to incorporate evaluations of co-design processes into study design.

A mixed-methods feasibility study of a goal-focused manualised intervention to support people with dementia to stay living independently at home with support from family carers: NIDUS (New Interventions for Independence in Dementia Study) Family.

OBJECTIVES: To examine the feasibility and acceptability of NIDUS-Family, a 6-8 session manualised, individually tailored, modular intervention supporting independence at home for people with dementia; and explore participants' and facilitators' experiences of the intervention. METHOD: In this single group multi-site feasibility study, trained, supervised non-clinically qualified graduates (facilitators) delivered NIDUS-Family to family carer and people living with dementia dyads. We recruited participants from GP practices and memory services in London and Bradford. We completed quantitative outcomes pre- and post-intervention; and conducted qualitative interviews with participants and facilitators. Our pre-specified main outcomes were proportion of potential participants approached who agreed to participate, intervention adherence and acceptability to family carers, and facilitator fidelity to the manual. RESULTS: We recruited 16 dyads (57% of those approached); 12 (75%) completed the intervention. Of 12 participants rating intervention acceptability, 9 (75%) agreed or strongly agreed that it had helped; 2 (18%) neither agreed nor disagreed and 1 (8%) disagreed. Mean facilitator fidelity was high (81.5%). Dyads set on average 3.9 goals; these most commonly related to getting out and about and increasing activity/hobby participation (n = 10); carer wellbeing (n = 6), managing physical complaints (n = 6); meal preparation/cooking (n = 5); and reducing irritability, frustration or aggression (n = 5). Almost all secondary outcomes changed in a direction indicating improvement. In our qualitative analysis we identified three overarching themes; relationships facilitate change, goal-focused versus manualised approach and balancing the needs of carers and people with dementia. CONCLUSION: NIDUS-Family was feasible and acceptable to participants. Following refinements, testing in a pragmatic trial is underway.

Recruiting hard to reach populations to studies: breaking the silence: an example from a study that recruited people with dementia.

OBJECTIVE: To share the challenges of recruiting people with dementia to studies, using experiences from one recently completed trial as an exemplar. BACKGROUND: Research publications always cite participant numbers but the effort expended to achieve the sample size is rarely reported, even when the study involved recruiting a hard to reach population. A multisite study of a psychosocial intervention for people with dementia illustrates the challenges. This study recruited 468 'dyads' (a person with dementia and a family carer together) from 15 sites but the time taken to achieve this was longer than originally estimated. This led to a study extension and the need for additional sites. Recruitment data revealed that certain sites were more successful than others, but why? Can the knowledge gained be used to inform other studies? METHODS: Secondary analysis of routinely collected recruitment data from three purposefully selected sites was examined to understand the strategies used and identify successful approaches. FINDINGS: At all three sites, the pool of potential recruits funnelled to a few participants. It took two sites 18 months longer than the third to achieve recruitment numbers despite additional efforts. Explanations given by potential participants for declining to take part included ill health, reporting they were 'managing', time constraints, adjusting to a diagnosis of dementia and burden of study procedures. CONCLUSIONS: Successful recruitment of people with dementia to studies, as one example of a hard to reach group, requires multiple strategies and close working between researchers and clinical services. It requires a detailed understanding of the needs and perspectives of the specific population and knowledge about how individuals can be supported to participate in research. Experiences of recruitment should be disseminated so that knowledge generated can be used to inform the planning and implementation of future research studies.

Euthanasia, religiosity and the valuation of health states: results from an Irish EQ5D5L valuation study and their implications for anchor values.

BACKGROUND: The Quality Adjusted Life Year influences the allocation of significant amounts of healthcare resources. Despite this surprisingly little research effort has been devoted to analysing how beliefs and attitudes to hastening death influence preferences for health states anchored at "dead" and "perfect health". In this paper we examine how, inter alia, adherence to particular religious beliefs (religiosity) influences attitudes to euthanasia and how, inter alia, attitudes to euthanasia influences the willingness to assign worse than dead (WTD) values to health states using data collected as part of the Irish EQ5D5L valuation study. METHODS: A sample of 160 respondents each supplied 10 composite time trade-off valuations and information on religiosity and attitudes to euthanasia as part of a larger national survey. Data were analysed using a recursive bivariate probit model in which attitudes to euthanasia and willingness to assign WTD values were analysed jointly as functions of a range of covariates. RESULTS: Religiosity was a significant determinant of attitudes to euthanasia and attitudes to euthanasia were a significant determinant of the likelihood of assigning WTD values. A significant negative correlation in errors between the two probit models was observed indicative of support for the hypothesis of endogeneity between attitudes to euthanasia and readiness to assign WTD values. CONCLUSION: In Ireland attitudes and beliefs play an important role in understanding health state preferences. Beyond Ireland this may have implications for: the construction of representative samples; understanding the values accorded health states and; the frequency with which value sets must be updated.

Analyzing self-similar and fractal properties of the C. elegans neural network.

The brain is one of the most studied and highly complex systems in the biological world. While much research has concentrated on studying the brain directly, our focus is the structure of the brain itself: at its core an interconnected network of nodes (neurons). A better understanding of the structural connectivity of the brain should elucidate some of its functional properties. In this paper we analyze the connectome of the nematode Caenorhabditis elegans. Consisting of only 302 neurons, it is one of the better-understood neural networks. Using a Laplacian Matrix of the 279-neuron "giant component" of the network, we use an eigenvalue counting function to look for fractal-like self similarity. This matrix representation is also used to plot visualizations of the neural network in eigenfunction coordinates. Small-world properties of the system are examined, including average path length and clustering coefficient. We test for localization of eigenfunctions, using graph energy and spacial variance on these functions. To better understand results, all calculations are also performed on random networks, branching trees, and known fractals, as well as fractals which have been "rewired" to have small-world properties. We propose algorithms for generating Laplacian matrices of each of these graphs.

SVM detection of epileptiform activity in routine EEG.

Routine electroencephalogram (EEG) is an important test in aiding the diagnosis of patients with suspected epilepsy. These recordings typically last 20-40 minutes, during which signs of abnormal activity (spikes, sharp waves) are looked for in the EEG trace. It is essential that events of short duration are detected during the routine EEG test. The work presented in this paper examines the effect of changing a range of input values to the detection system on its ability to distinguish between normal and abnormal EEG activity. It is shown that the length of analysis window in the range of 0.5s to 1s are well suited to the task. Additionally, it is reported that patient specific systems should be used where possible due to their better performance.

Cotranslational and posttranslational N-glycosylation of polypeptides by distinct mammalian OST isoforms.

Asparagine-linked glycosylation of polypeptides in the lumen of the endoplasmic reticulum is catalyzed by the hetero-oligomeric oligosaccharyltransferase (OST). OST isoforms with different catalytic subunits (STT3A versus STT3B) and distinct enzymatic properties are coexpressed in mammalian cells. Using siRNA to achieve isoform-specific knockdowns, we show that the OST isoforms cooperate and act sequentially to mediate protein N-glycosylation. The STT3A OST isoform is primarily responsible for cotranslational glycosylation of the nascent polypeptide as it enters the lumen of the endoplasmic reticulum. The STT3B isoform is required for efficient cotranslational glycosylation of an acceptor site adjacent to the N-terminal signal sequence of a secreted protein. Unlike STT3A, STT3B efficiently mediates posttranslational glycosylation of a carboxyl-terminal glycosylation site in an unfolded protein. These distinct and complementary roles for the OST isoforms allow sequential scanning of polypeptides for acceptor sites to insure the maximal efficiency of N-glycosylation.

Unique Asn-linked oligosaccharides of the human pathogen Entamoeba histolytica.

N-Glycans of Entamoeba histolytica, the protist that causes amebic dysentery and liver abscess, are of great interest for multiple reasons. E. histolytica makes an unusual truncated N-glycan precursor (Man(5)GlcNAc(2)), has few nucleotide sugar transporters, and has a surface that is capped by the lectin concanavalin A. Here, biochemical and mass spectrometric methods were used to examine N-glycan biosynthesis and the final N-glycans of E. histolytica with the following conclusions. Unprocessed Man(5)GlcNAc(2), which is the most abundant E. histolytica N-glycan, is aggregated into caps on the surface of E. histolytica by the N-glycan-specific, anti-retroviral lectin cyanovirin-N. Glc(1)Man(5)GlcNAc(2), which is made by a UDP-Glc: glycoprotein glucosyltransferase that is part of a conserved N-glycan-dependent endoplasmic reticulum quality control system for protein folding, is also present in mature N-glycans. A swainsonine-sensitive alpha-mannosidase trims some N-glycans to biantennary Man(3)GlcNAc(2). Complex N-glycans of E. histolytica are made by the addition of alpha1,2-linked Gal to both arms of small oligomannose glycans, and Gal residues are capped by one or more Glc. In summary, E. histolytica N-glycans include unprocessed Man(5)GlcNAc(2), which is a target for cyanovirin-N, as well as unique, complex N-glycans containing Gal and Glc.

The evolution of N-glycan-dependent endoplasmic reticulum quality control factors for glycoprotein folding and degradation.

Asn-linked glycans (N-glycans) play important roles in the quality control (QC) of glycoprotein folding in the endoplasmic reticulum (ER) lumen and in ER-associated degradation (ERAD) of proteins by cytosolic proteasomes. A UDP-Glc:glycoprotein glucosyltransferase glucosylates N-glycans of misfolded proteins, which are then bound and refolded by calreticulin and/or calnexin in association with a protein disulfide isomerase. Alternatively, an alpha-1,2-mannosidase (Mns1) and mannosidase-like proteins (ER degradation-enhancing alpha-mannosidase-like proteins 1, 2, and 3) are part of a process that results in the dislocation of misfolded glycoproteins into the cytosol, where proteins are degraded in the proteasome. Recently we found that numerous protists and fungi contain 0-11 sugars in their N-glycan precursors versus 14 sugars in those of animals, plants, fungi, and Dictyostelium. Our goal here was to determine what effect N-glycan precursor diversity has on N-glycan-dependent QC systems of glycoprotein folding and ERAD. N-glycan-dependent QC of folding (UDP-Glc:glycoprotein glucosyltransferase, calreticulin, and/or calnexin) was present and active in some but not all protists containing at least five mannose residues in their N-glycans and was absent in protists lacking Man. In contrast, N-glycan-dependent ERAD appeared to be absent from the majority of protists. However, Trypanosoma and Trichomonas genomes predicted ER degradation-enhancing alpha-mannosidase-like protein and Mns1 orthologs, respectively, each of which had alpha-mannosidase activity in vitro. Phylogenetic analyses suggested that the diversity of N-glycan-dependent QC of glycoprotein folding (and possibly that of ERAD) was best explained by secondary loss. We conclude that N-glycan precursor length has profound effects on N-glycan-dependent QC of glycoprotein folding and ERAD.

Dolichol-linked oligosaccharide selection by the oligosaccharyltransferase in protist and fungal organisms.

The dolichol-linked oligosaccharide Glc3Man9GlcNAc2-PP-Dol is the in vivo donor substrate synthesized by most eukaryotes for asparagine-linked glycosylation. However, many protist organisms assemble dolichol-linked oligosaccharides that lack glucose residues. We have compared donor substrate utilization by the oligosaccharyltransferase (OST) from Trypanosoma cruzi, Entamoeba histolytica, Trichomonas vaginalis, Cryptococcus neoformans, and Saccharomyces cerevisiae using structurally homogeneous dolichol-linked oligosaccharides as well as a heterogeneous dolichol-linked oligosaccharide library. Our results demonstrate that the OST from diverse organisms utilizes the in vivo oligo saccharide donor in preference to certain larger and/or smaller oligosaccharide donors. Steady-state enzyme kinetic experiments reveal that the binding affinity of the tripeptide acceptor for the protist OST complex is influenced by the structure of the oligosaccharide donor. This rudimentary donor substrate selection mechanism has been refined in fungi and vertebrate organisms by the addition of a second, regulatory dolichol-linked oligosaccharide binding site, the presence of which correlates with acquisition of the SWP1/ribophorin II subunit of the OST complex.

An evolving view of the eukaryotic oligosaccharyltransferase.

Asparagine-linked glycosylation (ALG) is one of the most common protein modification reactions in eukaryotic cells, as many proteins that are translocated across or integrated into the rough endoplasmic reticulum (RER) carry N-linked oligosaccharides. Although the primary focus of this review will be the structure and function of the eukaryotic oligosaccharyltransferase (OST), key findings provided by the analysis of the archaebacterial and eubacterial OST homologues will be reviewed, particularly those that provide insight into the recognition of donor and acceptor substrates. Selection of the fully assembled donor substrate will be considered in the context of the family of human diseases known as congenital disorders of glycosylation (CDG). The yeast and vertebrate OST are surprisingly complex hetero-oligomeric proteins consisting of seven or eight subunits (Ost1p, Ost2p, Ost3p/Ost6p, Ost4p, Ost5p, Stt3p, Wbp1p, and Swp1p in yeast; ribophorin I, DAD1, N33/IAP, OST4, STT3A/STT3B, Ost48, and ribophorin II in mammals). Recent findings from several laboratories have provided overwhelming evidence that the STT3 subunit is critical for catalytic activity. Here, we will consider the evolution and assembly of the eukaryotic OST in light of recent genomic evidence concerning the subunit composition of the enzyme in diverse eukaryotes.

Mapping the interaction of the STT3 subunit of the oligosaccharyl transferase complex with nascent polypeptide chains.

Many secretory and membrane proteins are N-glycosylated by the oligosaccharyl transferase complex during their translocation across the endoplasmic reticulum membrane. Several experimental observations suggest that the highly conserved STT3 subunit contains the active site of the oligosaccharyl transferase. Here, we report a detailed study of the interaction between the active site of the STT3 protein and nascent polypeptide chains using an in vitro photocrosslinking technique. Our results show that the addition of a glycan moiety in a stretch of approximately 15 residues surrounding a QK(*)T cross-linking site impairs the interaction between the nascent chain and STT3.

The diversity of dolichol-linked precursors to Asn-linked glycans likely results from secondary loss of sets of glycosyltransferases.

The vast majority of eukaryotes (fungi, plants, animals, slime mold, and euglena) synthesize Asn-linked glycans (Alg) by means of a lipid-linked precursor dolichol-PP-GlcNAc2Man9Glc3. Knowledge of this pathway is important because defects in the glycosyltransferases (Alg1-Alg12 and others not yet identified), which make dolichol-PP-glycans, lead to numerous congenital disorders of glycosylation. Here we used bioinformatic and experimental methods to characterize Alg glycosyltransferases and dolichol-PP-glycans of diverse protists, including many human pathogens, with the following major conclusions. First, it is demonstrated that common ancestry is a useful method of predicting the Alg glycosyltransferase inventory of each eukaryote. Second, in the vast majority of cases, this inventory accurately predicts the dolichol-PP-glycans observed. Third, Alg glycosyltransferases are missing in sets from each organism (e.g., all of the glycosyltransferases that add glucose and mannose are absent from Giardia and Plasmodium). Fourth, dolichol-PP-GlcNAc2Man5 (present in Entamoeba and Trichomonas) and dolichol-PP- and N-linked GlcNAc2 (present in Giardia) have not been identified previously in wild-type organisms. Finally, the present diversity of protist and fungal dolichol-PP-linked glycans appears to result from secondary loss of glycosyltransferases from a common ancestor that contained the complete set of Alg glycosyltransferases.

Oligosaccharyltransferase isoforms that contain different catalytic STT3 subunits have distinct enzymatic properties.

Oligosaccharyltransferase (OST) is an integral membrane protein that catalyzes N-linked glycosylation of nascent proteins in the lumen of the endoplasmic reticulum. Although the yeast OST is an octamer assembled from nonhomologous subunits (Ost1p, Ost2p, Ost3p/Ost6p, Ost4p, Ost5p, Wbp1p, Swp1p, and Stt3p), the composition of the vertebrate OST was less well defined. The roles of specific OST subunits remained enigmatic. Here we show that genomes of most multicellular eukaryotes encode two homologs of Stt3p and mammals express two homologs of Ost3p. The Stt3p and Ost3p homologs are assembled together with the previously described mammalian OST subunits (ribophorins I and II, OST48, and DAD1) into complexes that differ significantly in enzymatic activity. Tissue and cell type-specific differences in expression of the Stt3p homologs suggest that the enzymatic properties of oligosaccharyltransferase are regulated in eukaryotes to respond to alterations in glycoprotein flux through the secretory pathway and may contribute to tissue-specific glycan heterogeneity.

Photocross-linking of nascent chains to the STT3 subunit of the oligosaccharyltransferase complex.

In eukaryotic cells, polypeptides are N glycosylated after passing through the membrane of the ER into the ER lumen. This modification is effected cotranslationally by the multimeric oligosaccharyltransferase (OST) enzyme. Here, we report the first cross-linking of an OST subunit to a nascent chain that is undergoing translocation through, or integration into, the ER membrane. A photoreactive probe was incorporated into a nascent chain using a modified Lys-tRNA and was positioned in a cryptic glycosylation site (-Q-K-T- instead of -N-K-T-) in the nascent chain. When translocation intermediates with nascent chains of increasing length were irradiated, nascent chain photocross-linking to translocon components, Sec61alpha and TRAM, was replaced by efficient photocross-linking solely to a protein identified by immunoprecipitation as the STT3 subunit of the OST. No cross-linking was observed in the absence of a cryptic sequence or in the presence of a competitive peptide substrate of the OST. As no significant nascent chain photocross-linking to other OST subunits was detected in these fully assembled translocation and integration intermediates, our results strongly indicate that the nascent chain portion of the OST active site is located in STT3.