Population Of Chl Research Articles

Pembrolizumab (pembro) in Children and Young Adults with High-Risk Classical Hodgkin Lymphoma (cHL) with Slow Early Response (SER) to Front-Line Chemotherapy (chemo): Updated Results from the Phase 2 Keynote-667 Study

Background: cHL is one of the most curable forms of childhood cancer, but patients (pts) who have a SER to initial chemo are at high risk of relapse. The approaches currently used to treat pts with SER, such as dose intensification and radiotherapy (RT), can cause long-term toxicity.An unmet need remains to optimize treatment in pts with cHL and SER while minimizing long-term toxicity. The open-label, phase 2 KEYNOTE-667 study (NCT03407144) is being conducted to evaluate the efficacy and safety of pembro plus chemo in pediatric pts with cHL and SER to front-line chemo. Early analysis of pts in KEYNOTE-667 with high-risk cHL showed that pembro plus cyclophosphamide, vincristine, prednisone/prednisolone, and dacarbazine (COPDAC-28) consolidation had manageable safety and promising antitumor activity, with 66% of pts being spared RT. We present updated results for pts with high-risk cHL and SER. Methods: Pts eligible for the high-risk group were 3-25 y old and had newly diagnosed stage IIEB, IIIEA, IIIEB, IIIB, IVA, or IVB cHL, measurable disease per investigator assessment, and a Lansky Play-Performance Scale ≥50 (<16 y old) or a Karnofsky score ≥50 (≥16 y old). All pts received 2 cycles of induction therapy with vincristine, etoposide, prednisone/prednisolone, and doxorubicin (OEPA). After induction, response was assessed by PET/MRI/CT (early response assessment). Pts with rapid early response received nonstudy therapy. Pts with SER (Deauville score, 4 or 5) received consolidation with pembro 2 mg/kg up to 200 mg IV Q3W (3-17 y) or 200 mg IV Q3W (18-25 y) plus 4 cycles of COPDAC-28. Response was then assessed by PET/CT/MRI (late response assessment [LRA]). Pts with PET positivity at LRA (Deauville score, 4 or 5) received involved-site RT (28.8 Gy) to late PET-positive residua plus maintenance pembro Q3W for up to 17 cycles; pts with PET negativity received maintenance pembro Q3W for up to 17 cycles without RT. The primary end point was ORR by BICR per Cheson 2007 IWG criteria in pts with SER, determined at any time after starting pembro and before start of new anticancer therapy. Secondary end points included PET negativity after consolidation, EFS, OS, and safety. Results: This analysis included 62 pts with high-risk cHL and SER to frontline OEPA. The median time from enrollment to data cutoff (March 1, 2023) was 16.8 mo (range, 2.3-36.4). At the data cutoff, 34 pts (55%) had completed consolidation and maintenance therapy, 23 (37%) were ongoing on treatment, and 5 (8%) had discontinued because of adverse events (AEs; n = 1), progressive disease (n = 2), or withdrawal by pt (n = 2). Median age was 14 y (range, 5-22), 30 pts (48%) were male, 29 (47%) had bulky disease, and 41 (66%) had Ann Arbor stage IV disease. Pts had received a median of 17 administrations of pembro (range, 1-17); the median time on pembro was 11.0 mo (range, <0.1-11.8). Of 62 pts who received consolidation with pembro plus COPDAC-28, 53 (85%) had a LRA (9 are still in consolidation and have not reached the LRA time point), of whom 35 (66%) were PET negative by BICR (37 [70%] PET negative by investigator review). AEs regardless of causality that occurred during consolidation and maintenance were reported in 54 pts (87%), most commonly (≥15%) headache (n = 11; 18%), nausea (n = 11; 18%), cough (n = 10; 16%), COVID-19 (n = 10; 16%), and pyrexia (n = 10; 16%). Grade 3/4 AEs occurred in 21 pts (34%). 13 pts (21%) had a serious AE. No pts died because of AEs. Treatment-related AEs occurred in 38 pts (61%). Grade 3/4 treatment-related AEs occurred in 10 pts (16%). One pt (2%) discontinued treatment because of a treatment-related AE (grade 3 AST increased). Pembro-related AEs occurred in 23 (37%) pts; most commonly (≥5%) hypothyroidism (n = 4; 6%), nausea (n = 3; 5%), and ALT increased (n = 3; 5%). Three pts (5%) experienced grade 3/4 pembro-related AEs. One serious AE was related to pembro (abdominal pain). Six pts (10%) experienced immune-mediated AEs (hypothyroidism, n = 4 [2 grade 1, 2 grade 2]; colitis, n = 1 [grade 2]; pneumonitis, n = 1 [grade 2]). Conclusion: In this updated analysis, consolidation with pembro plus COPDAC-28 continued to have manageable safety and promising antitumor activity in pediatric pts with high-risk cHL and SER to front-line OEPA. Of pts with a LRA, 66% had a PET-negative response and were spared RT. These findings support the results of prior analyses and suggest that adding pembro to COPDAC-28 consolidation may augment responses in the high-risk cHL population.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Introduction: Patients (pts) with cHL with slow early response (SER) to initial chemotherapy (chemo) have a high risk of relapse. Current treatments such as chemo dose intensification and radiotherapy (RT) can increase the risk of secondary malignancies and cause long-term toxicity. KEYNOTE-667 (NCT03407144) is an open-label, phase 2 study being conducted to evaluate pembrolizumab (pembro) plus chemo in pts with cHL and SER to front-line chemo. We present results of an interim analysis of pts with high-risk cHL and SER (group 2). Methods: Pts eligible for group 2 were aged 3–17 (children) or 18–25 y (young adults) with newly diagnosed high-risk (stage IIEB, IIIEA, IIIEB, IIIB, IVA, or IVB) cHL. Pts in group 2 received induction therapy with 2 cycles of vincristine, etoposide, prednisone/prednisolone, and doxorubicin (OEPA). Response was then assessed by PET/MRI/CT. Pts with rapid early response to OEPA received nonstudy therapy and pts with SER to OEPA (Deauville score, 4/5) received consolidation with 4 cycles of cyclophosphamide, vincristine, prednisone/prednisolone, dacarbazine (COPDAC-28) plus pembro 2 mg/kg up to 200 mg IV Q3W (3–17 y) or 200 mg IV Q3W (18–25 y). After consolidation, pts with PET positivity (Deauville score, 4/5 at late response assessment [LRA]) received involved-site RT (28.8 Gy) to late PET-positive residua. RT was omitted in pts with PET negativity. All pts with SER continued to receive pembro Q3W for 17 doses. The primary end point was ORR in pts with SER by blinded independent central review (BICR) per Cheson 2007 International Working Group criteria. Secondary end points included PET negativity at LRA and safety. Results: 49 pts with high-risk cHL with SER to OEPA were included in group 2. The median age was 15 y (range, 6–22), 24 pts (49%) had bulky disease, and 31 (63%) had Ann Arbor stage IV disease. At data cutoff (2 September 2022), the median follow-up was 15.3 mo (range, 3.2–30.5); 22 pts (45%) had completed treatment and 24 (49%) were ongoing on consolidation/maintenance. Median time on pembrolizumab was 10.4 mo (range, 0.5–11.8). 42 pts (86%) had an LRA, of whom 27 (64%) were PET negative by BICR (30 pts [71%] were PET negative by investigator review). Adverse events (AEs) occurred in 42 pts (86%), with grade 3/4 AEs in 13 pts (27%). Serious AEs were reported in 7 pts (14%). No pts died because of an AE. Treatment-related AEs occurred in 30 pts (61%), with grade 3/4 treatment-related AEs in 6 pts (12%). 4 pts (8%) had immune-mediated AEs: 2 grade 1 hypothyroidism and 2 grade 2 hypothyroidism. Conclusions: The results showed that pembro plus COPDAC-28 consolidation had manageable safety and promising efficacy in children and young adults with high-risk cHL and SER to front-line chemo. 64% of pts with a LRA had a PET-negative response and were spared RT. These findings suggest that adding pembro to COPDAC-28 consolidation may augment responses in this high-risk cHL population. Encore Abstract - previously submitted to ASCO 2023 and EHA 2023 The research was funded by: Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA Keywords: Hodgkin lymphoma, immunotherapy Conflicts of interests pertinent to the abstract L. Vinti Consultant or advisory role: Amgen, Clinigen Research funding: Merck, Sharp & Dohme Educational grants: Takeda, Neon Other remuneration: Amgen, Takeda F. Fagioli Employment or leadership position: Takeda, Novartis, Jazz Pharmaceuticals, Sanofi Consultant Or Advisory Role: Takeda, Novartis, Jazz Pharmaceuticals, Sanofi Honoraria: Takeda, Novartis, Jazz Pharmaceuticals, Sanofi Educational Grants: Takeda, Novartis, Jazz Pharmaceuticals, Sanofi Other Remuneration: Takeda, Novartis, Jazz Pharmaceuticals, Sanofi D. Plaza Lopez de Sabando Research funding: MERCK J. Landman-Parker Research funding: BMS, MSD J. Shen Employment or leadership position: Merck P. Pillai Employment or leadership position: Merck Stock ownership: Merck P. Marinello Employment or leadership position: Merck Stock ownership: Merck C. Mauz-Koerholz Consultant or advisory role: MSD Research funding: MSD

Association of Epstein-Barr Virus with Advanced Stage and Survival Outcomes in Classic Hodgkin's Lymphoma

Association of Epstein-Barr Virus with Advanced Stage and Survival Outcomes in Classic Hodgkin's Lymphoma

Chlorophyll a with a farnesyl tail in thermophilic cyanobacteria

Photosystem II (PSII) of oxygenic photosynthetic organisms normally contains exclusively chlorophyll a (Chl a) as its major light-harvesting pigment. Chl a canonically consists of the chlorin headgroup with a 20-carbon, 4-isoprene unit, phytyl tail. We have examined the 1.9Å crystal structure of PSII from thermophilic cyanobacteria reported by Shen and coworkers in 2012 (PDB accession of 3ARC/3WU2). A newly refined electron density map from this structure, presented here, reveals that some assignments of the cofactors may be different from those modeled in the 3ARC/3WU2 structure, including a specific Chl a that appears to have a truncated tail by one isoprene unit. We provide experimental evidence using high-performance liquid chromatography and mass spectrometry for a small population of Chl a esterified to a 15-carbon farnesyl tail in PSII of thermophilic cyanobacteria.

Heterogeneity of grain-size fractions of nanodiamonds from the Orgueil C1 meteorite

A model for the composition of meteoritic nanodiamonds is suggested based on analysis of the concentrations and isotopic compositions of C, N, and Xe in the nanodiamond-rich grain-size fractions, which were separated for the first time from the Orgueil CI chondrite. According to the model, meteoritic nanodiamond consists of two populations of grains (denoted CHL and CN). The size distributions of grains in populations in the CHL and CN populations are different: the CHL population is finer grained than CN. The grains of the CHL population are characterized by a radial gradient in the carbon isotopic composition, and they contain implanted anomalous noble gases (HL component) and the heavy nitrogen isotope 15N. Following (Clayton et al., 1995), the probable astrophysical source of this population of nanodiamond grains is thought to be the mixing helium and hydrogen shells of a Type-II supernova, and the mechanism that produced these grains was the slow CVD process. The CN population grains have homogeneous isotopic compositions of carbon (δ13C ≡–100‰) and nitrogen (δ15N ≡–400‰) and contain almost all nitrogen of the nanodiamond-rich fractions. This population of nanodiamond grains was likely formed by a fast unequilibrated process, when shock waves affected organic compounds or gas rich in C- and N-bearing compounds during the early evolution of the protosolar nebula. Calculations within the framework of the model show that the nanodiamond-rich fractions separated from the Orgueil meteorite have the CN/CHL ratios varying from 1 in the finest grained fraction to 10 in the coarse-grained one. At these proportions of the populations, weighted mean δ13C values of CHL grains in the fractions lie within the range of 42 to 394‰, and the concentrations of 132Xe-HL and 15N are (49–563) × 10–8 cm3/gC and (1.1–6.2) × 10–5 cm3/gC, respectively.

HLA associations in classical Hodgkin lymphoma: EBV status matters.

The pathogenesis of classical Hodgkin lymphoma (cHL) involves environmental and genetic factors. To explore the role of the human leukocyte antigen (HLA) genes, we performed a case-control genotyping study in 338 Dutch cHL patients using a PCR-based sequence-specific oligonucleotide probe (SSOP) hybridization approach. The allele frequencies were compared to HLA typings of more than 6,000 controls. The age of the cHL patients varied between 13 and 81 years with a median of 35 years. Nodular sclerosis subtype was the most common subtype (87%) and EBV was detected in 25% of the cHL patients. HLA-B5 was significantly increased and HLA-DR7 significantly decreased in the total cHL patient population as compared to controls. Two class II associations were observed to be specific for the EBV− cHL population with an increase of HLA-DR2 and HLA-DR5. Allele frequencies of HLA-A1, HLA-B37 and HLA-DR10 were significantly increased in the EBV+ cHL population; these alleles are in strong linkage disequilibrium and form a common haplotype in Caucasians. The allele frequency of HLA-A2 was significantly decreased in the EBV+ cHL population. Analysis of haplotypes with a frequency of >1% revealed a significant increase of HLA-A2-B7-DR2 in EBV− cHL as compared to controls. SSOP association analysis revealed significant differences between EBV+ and EBV− cHL patients for 19 probes that discriminate between HLA-A*01 and HLA-A*02. In conclusion, the HLA-A1 and HLA-A2 antigens and not specific single nucleotide variants shared by multiple alleles are responsible for the association with EBV+ cHL. Furthermore several new protective and predisposing HLA class I and II associations for the EBV+, the EBV− and the entire cHL population were identified.

Huang X, Kushekhar K, Nolte I, Kooistra W, Visser L, Bouwman I, Kouprie N, Veenstra R, van Imhoff G, Olver B, Houlston RS, Poppema S, Diepstra A, Hepkema B, van den Berg A. Multiple HLA class I and II associations in classical Hodgkin lymphoma and EBV status defined subgroups. Blood. 2011;118(19):5211–5217.

The pathogenesis of classical Hodgkin lymphoma (cHL) involves environmental and genetic factors. To explore the role of the human leukocyte antigen (HLA) genes, we performed a case-control genotyping study in 338 Dutch cHL patients and more than 5000 controls using a PCR-based sequence-specific oligonucleotide probe hybridization approach. HLA-A68 and HLA-DR11 (5) were significantly increased in the cHL patient population compared with the controls. Three class II associations were observed in the EBV- cHL population with an increase of HLA-DR15 (2) and a decrease of HLA-DR4 and HLA-DR7. Allele frequencies of HLA-A1, HLA-B37, and HLA-DR10 were significantly increased in the EBV+ cHL population; these alleles are in strong linkage disequilibrium and form a common haplotype in whites. The allele frequency of HLA-A2 was significantly decreased in the EBV- cHL population. Sequence-specific oligonucleotide probe analysis revealed significant differences between EBV+ and EBV- cHL patients for 19 probes that discriminate between HLA-A*01 and HLA-A*02. In conclusion, the HLA-A1 and HLA-A2 antigens and not specific single nucleotide variants shared by multiple alleles are responsible for the association with EBV+ cHL. Furthermore, several new protective and predisposing HLA class I and II associations for the EBV+, the EBV-, and the entire cHL population were identified. (Blood. 2011;118(19):5211-5217)

Multiple HLA class I and II associations in classical Hodgkin lymphoma and EBV status defined subgroups

AbstractThe pathogenesis of classical Hodgkin lymphoma (cHL) involves environmental and genetic factors. To explore the role of the human leukocyte antigen (HLA) genes, we performed a case-control genotyping study in 338 Dutch cHL patients and more than 5000 controls using a PCR-based sequence-specific oligonucleotide probe hybridization approach. HLA-A68 and HLA-DR11 (5) were significantly increased in the cHL patient population compared with the controls. Three class II associations were observed in the EBV− cHL population with an increase of HLA-DR15 (2) and a decrease of HLA-DR4 and HLA-DR7. Allele frequencies of HLA-A1, HLA-B37, and HLA-DR10 were significantly increased in the EBV+ cHL population; these alleles are in strong linkage disequilibrium and form a common haplotype in whites. The allele frequency of HLA-A2 was significantly decreased in the EBV+ cHL population. Sequence-specific oligonucleotide probe analysis revealed significant differences between EBV+ and EBV− cHL patients for 19 probes that discriminate between HLA-A*01 and HLA-A*02. In conclusion, the HLA-A1 and HLA-A2 antigens and not specific single nucleotide variants shared by multiple alleles are responsible for the association with EBV+ cHL. Furthermore, several new protective and predisposing HLA class I and II associations for the EBV+, the EBV−, and the entire cHL population were identified.

Epidemiology of Classical Hodgkin Lymphoma and Its Association with Epstein Barr Virus in Northern China

BackgroundThe incidence of classical Hodgkin lymphoma (cHL) and its association with Epstein-Barr virus (EBV) varies significantly with age, sex, ethnicity and geographic location. This is the first report on epidemiological features of cHL patients from Northern regions of China. These features are compared to data from a previously published Dutch cHL population.Methodology/Principal Findings157 cHL patients diagnosed between 1997 and 2008 in the North of China were included after histopathological re-evaluation. The Dutch population-based cohort consisted of 515 cHL patients diagnosed between 1987 and 2000. EBV status was determined by in situ hybridization of EBV- encoded small RNAs. In the Chinese population, tumor cells of 39% of the cHL patients were EBV+ and this was significantly associated with male sex, mixed cellularity subtype and young age (<20 y). The median age of the Chinese patients was 9 years younger than that of the Dutch patients (28 y vs. 37 y). In addition, the age distribution between the two populations was strikingly different in both the EBV+ subgroups (p<0.001) and the EBV- subgroups (p = 0.01). The mixed cellularity subtype was almost 3x more frequent amongst the Chinese (p<0.001).Conclusion/SignificanceCHL patients from Northern regions of China show a distinctive age distribution pattern with a striking incidence peak of EBV+ mixed cellularity cases among children and adolescents and another high incidence peak of EBV- nodular sclerosis cases in young adults. In comparison to Dutch cHL patients there are pronounced differences in age distribution, subtype and EBV status, presumably caused by complex gene-environmental interactions.

Intra- and inter-monomeric transfers in the light harvesting LHCII complex: the Redfield–Förster picture

We further develop the model of energy transfer in the LHCII trimer based on a quantitative fit of the linear spectra (including absorption (OD), linear dichroism (LD), circular dichroism (CD), and fluorescence (FL)) and transient absorption (TA) kinetics upon 650 nm and 662 nm excitation. The spectral shapes and relaxation/migration rates have been calculated using the combined Redfield-Förster approach capable of correctly describing fast relaxation within strongly coupled chlorophyll (Chl) a and b clusters and slow migration between them. Within each monomeric subunit of the trimeric complex there is fast (sub-ps) conversion from Chl's b to Chl's a at the stromal side accompanied by slow (>10 ps) equilibration between the stromal- and lumenal-side Chl a clusters in combination with slow (>13 ps) population of Chl's a from the 'bottleneck' Chl a604 site. The connection between monomeric subunits is determined by exciton coupling between the stromal-side Chl's b from the two adjacent subunits (Chl b601'-608-609 cluster) making a simultaneous fast (sub-ps) population of the Chl's a possible from both subunits. Final equilibration occurs via slow (>20 ps) migration between the Chl a clusters located on different monomeric subunits. This migration includes up-hill transfers from the red-most Chl a610-611-612 clusters located at the peripheral side in each subunit to the Chl a602-603 dimers located at the inner side of the trimeric LHCII complex.

Protective and Predisposing HLA Alleles In Dutch Classical Hodgkin Lymphoma Patients

AbstractAbstract 749Classical Hodgkin lymphoma (cHL) is characterized by an overwhelming reactive infiltrate and the involvement of Epstein Barr virus (EBV) as a causative agent in a proportion of patients. We previously did a population-based genetic screening study of the Human Leukocyte Antigen (HLA) region in Dutch cHL patients and found a strong association between HLA class I (HLA-A1) and susceptibility to EBV+ cHL. This association might be explained by the known lack of HLA-A1 restricted T cell responses to EBV latent antigens. We now performed a case-control study to determine allele frequencies of all major HLA class I and class II genes in this cHL population. HLA genotyping of 294 cHL patients was performed by a polymerase chain reaction-based sequence-specific oligonucleotide probe hybridization (PCR-SSOP) approach in Luminex assays. The resulting single nucleotide polymorphism (SNP) data were converted into two-digit HLA typing for the HLA class I and class II genes. Phenotype frequencies of serologically defined HLA-A, HLA-B and HLA-DR blood donors were retrieved from the database of the blood bank of the University Medical Center Groningen. Allele frequency differences between these controls and cHL patients (total group and EBV+ and EBV- subgroups separately) were analyzed by Chi-square tests. In addition, we analyzed the HLA genotyping data for every PCR-SSOP probe to assess potential differences between the EBV+ and EBV- cHL group using PLINK software. Frequencies of HLA-DR4 and HLA-DR7 were significantly decreased and HLA-B5 and HLA-B37 were significantly increased in cHL as compared to the controls. In EBV+ cHL, HLA-A1, HLA-B37 and HLA-DR10 frequencies were significantly increased and HLA-A2 was decreased. An increase in HLA-B8, an allele that can present EBV peptides and that usually is in strong linkage disequilibrium with HLA-A1, was not present in these patients. In EBV- cHL, HLA-DR5 was significantly more common and HLA-DR4 was underrepresented. The SNP analysis revealed significant differences for 16 HLA-A probes between EBV+ and EBV- cHL. Eight probes that represented a high susceptibility for EBV+ cHL were specific for HLA-A1, whereas the other 8 probes correlated with a low risk for EBV+ cHL and were specific for HLA-A2. Most of the corresponding SNPs had a presumed antigenic peptide or T cell receptor binding function. In conclusion, the current study demonstrates that certain HLA alleles are protective or predisposing for cHL with specific associations for the EBV+ and EBV- cHL subgroups. The genotype analysis indicates that the complete HLA-A1 and HLA-A2 alleles are more important than individual T-cell receptor or antigen binding polymorphisms for the association with EBV+ cHL. Disclosures:No relevant conflicts of interest to declare.

Populations of nanodiamond grains in meteorites from the data on isotopic composition and content of nitrogen

The present study has shown that the dependence of the isotopic composition of nitrogen on the N/C ratio, revealed from the data for bulk samples of meteoritic nanodiamond, can be obtained within the framework of the following model of the composition of populations of nanodiamond grains: (a) initial nanodiamond, i.e., the nanodiamond in the protoplanetary cloud before the accretion of the meteorite parent bodies, was composed mainly of grains of two populations (denoted as CN and CF), the ratio of which changed in meteorites depending on the degree of hydrothermal metamorphism; (b) only the grains of one of these populations (CN) contain volume-bound nitrogen with δ15N = −350‰; (c) the grains of both populations contain surface-bound nitrogen (δ15N ≡ 0). The calculations revealed the following properties of population grains in this model. (1) The grains of the CN and CF populations are most likely the same in isotopic composition of carbon and heterogeneous in distribution of its isotopes: the central part of grains is enriched with the δ12C isotope relative to the remainder of the grain. While the value of δ13C is −37.3 ± 1.1‰ for carbon in the central part, it is −32.8 ± 1.5‰ for the whole volume of the grains. (2) The noble gases of the HL component, specifically Xe-HL, are anomalous in isotopic composition and are most likely contained in the third population of nanodiamond grains (denoted as CHL), the mass fraction of which is negligible relative to that for other grain populations. Only the grains of the CHL population have an undoubtedly presolar origin, while the grains of the other nanodiamond populations could have formed at the early stages of the evolution of the protoplanetary cloud material before the accretion of the meteoritic parent bodies.

Pigment‐Protein Interactions in the Antenna‐Reaction Center Complex of Heliobacillus mobilis

AbstractMembrane fragments of Heliobacillus (Hc.) mobilis were characterized using resonance Raman (RR) spectroscopy in order to determine the configuration of the neurosporene carotenoid, the pigment‐protein interactions of the bacteriochlorophyll (BChl) g molecules, and the Chl a‐like chlorin pigments present in the antenna‐reaction center complex constituting the photosynthetic apparatus. Using 363.8 nm excitation, the Raman contributions of the BChl g molecules were selectively resonantly enhanced over those of the carotenoid and the Chl a‐like chlorin pigments. The RR spectrum of BChl g in these membranes excited at 363.8 nm exhibits bands at 1614 and 1688 cm−1, which correspond to a CaCm methine bridge stretching mode and a keto carbonyl group stretching mode, respectively. Both of these bands are 16 cm−1 wide (full width at half maximum, FWHM), indicating that a sole population of BChl g molecules is being enhanced at this excitation wavelength. The observed frequency of the CaCm stretching mode (1614 cm−1) indicates that the bulk of BChl g molecules is pentacoordinated with only one axial ligand to the central Mg atom while that of the keto carbonyl stretching mode (1668 cm−1) indicates that these groups are engaged in a hydrogen bond. This homogeneous population of BChl g molecules bound to the heliobacterial core polypeptides is in contrast to the heterogeneous population of Chl a molecules bound to the core polypeptides of the reaction center of photosystem I of Synechocystis 6803 as observed by the inhomogeneously broadened C9 keto carbonyl band in its RR spectrum. The RR spectrum of the Chl a‐like chlorin pigments in Hc. mobilis excited at 441.6 nm exhibits a broad keto carbonyl band (43 cm−1 FWHM) with components at 1665, 1683 and 1695 cm−1, indicating several populations of these pigments differing in their protein interactions at the level of the keto carbonyl group. Fourier transform (FT) pre‐RR spectroscopic measurements of intact whole cells and membrane fragments at room temperature using 1064 nm excitation indicate that high quality vibrational spectra of the BChl g molecules can be obtained with no photodegradation. Low‐temperature FT Raman spectra excited at 1064 nm reveals an inhomogeneously broadened 1665 cm−1 band corresponding to the C9 keto carbonyl stretching mode. Spectral deconvolution and second derivative analysis of this band reveal that it is comprised of components at 1665, 1682 and 1695 cm−1, the latter two most likely arising from BChl g photoconversion products. Excitation using 885 nm to enhance the preresonance effect of the BChl g molecules yields an FT Raman spectrum where the keto carbonyl band at 1665 cm−1 is narrow, as is the case in the Soret RR spectra, reflecting a sole population of BChl g molecules, which are engaged in an H bond. The RR spectrum of the neurosporene molecule in Hc. mobilis membranes excited at 496.5 nm is compared to that of 1,2‐dihydroneurosporene bound in a cis configuration in reaction centers of Rhodopseudomona viridis and to that of the same carotenoid in its all‐trans configuration extracted from these reaction centers in the presence of light. The similarity of this latter RR spectrum with that of neurosporene in the Hc. mobilis membranes indicates that it is bound in an all‐trans configuration.