31 Refractometry & Polarimetry


The comprehensive and audit-proven qualifi cation documents from Anton Paar streamline the qualifi cation process, reducing the workload for in-house personnel by up to 70%.


This simplifi es the qualifi cation process and helps you attain and retain system productivity more quickly.


Enjoy the complete package of professional instrument and system qualifi cation to integrate the instrument quickly into your workfl ow and guidelines.


• FDA 4Q model: covering design, installation, and operational and performance qualifi cations


• Risk assessment: addressing potential compliance issues


• 21 CFR Part 11 compliance: ensuring software and systems meet stringent regulatory standards


• Traceability and reporting: facilitating audit readiness with traceability matrices and qualifi cation summaries


Table 1: Overview of amino acids.


Essential AA Obtained from Nutrition


Leucine


Isoleucine Histidin


Lysine Methionine Phenylalanine


Threonine Tryptophan Valine


Practical considerations


Each amino acid comprises two different forms called the L- and D-form. The L-form of amino acids is usually the biologically reactive form.


Being a zwitterion, a molecule with an equal number of positively and negatively charged functional groups, the overall charge of an amino acid strongly depends on the pH value. These characteristics affect the molecule’s geometrical structure and therefore also the optical rotation of the light


The specifi c rotation [a] 20 is a measure of the optical rotation (α) at a defi ned concentration (c) of 1 g / 100 mL, a path length (sodium D line), and a temperature of 20°C:


D of 1 dm, a wavelength of 589 nm


As a result, international pharmacopoeias require the measurement of amino acids in defi ned acidic or basic solutions, to assure the generation of comparable results; see an example in Figure 1.


SPECIFIC TESTS Training and adoption: Empowering users


Successful adoption of new technology depends heavily on user acceptance and proper training.


Training programs: Polarimeters are easy to operate and almost self-explaining. However, comprehensive training for laboratory personnel on using polarimeters ensures accurate and reliable measurements.


Ease of adoption: Due to its straightforward operation, polarimetry can be quickly learned and integrated into daily laboratory routines, minimising disruption.


• Embedded and desktop software allows fl exible confi guration to seamlessly adapt to existing SOPs.


Application: polarimetric analysis of amino acids Amino acids as optically active zwitterions


Ÿ Optical Rotation, Specific Rotation (781S) Sample solution: 80 mg/mL in 6 N hydrochloric acid Acceptance criteria: +24.0° to +26.0°, at 20°


Figure 1: Determination of the specific rotation of L-aspartic acid according to the US Pharmacopeia.


Use of amino acids in biopharmaceuticals


Biopharmaceuticals, often referred to as biologics, represent a revolutionary class of medicines that rely on biological systems to produce therapeutic or diagnostic substances. These protein- or nucleic acid-based pharmaceuticals are at the forefront of modern medicine, addressing complex diseases with unmatched precision.


What Are Biopharmaceuticals?


Biopharmaceuticals are pharmaceutical substances derived from living organisms. Unlike conventional drugs that are chemically synthesised, biopharmaceuticals are produced using genetically modifi ed cells such as bacteria, yeast, animal or human cells, or even plants. These cells are engineered to produce therapeutic compounds encoded by inserted genetic material.


One of the most signifi cant advancements in this fi eld is recombinant protein expression. This technique involves the insertion of human DNA into a host organism, enabling it to produce peptides or proteins identical to their human counterparts. For example, the production of insulin – a peptide hormone crucial for regulating blood sugar – has been revolutionised by this method.


The importance of amino acids in biopharmaceuticals


Amino acids are the fundamental building blocks of proteins, and their role in biopharmaceuticals is indispensable. Every biopharmaceutical protein is composed of a specifi c sequence of amino acids, which determines its structure and function. The precision with which these amino acids are assembled is critical for the therapeutic effi cacy and safety of the fi nal product.


More than 50 years ago, amino acids were found to be an important component in metabolism. That’s why they play a major role in the pharmaceutical and food industry. Amino acids, as optically active compounds, are frequently analysed using polarimetry to determine their purity and concentration. For example, L-glutamine, a key amino acid used in pharmaceutical formulations and nutritional supplements, exhibits specifi c optical rotation values under defi ned conditions.


In recent times, the biopharmaceutical industry has been growing strongly, and amino acids are a key ingredient, e.g., for recombinant proteins.


Amino acids are a group of organic compounds, classifi ed into essential and non- essential (Table 1). Essential amino acids cannot be synthesised within the human body; they have to be taken from outside sources in animal or plant food forms.


Key aspects of amino acids in biopharmaceuticals include:


1. Protein structure and stability: The sequence and arrangement of amino acids determine the three-dimensional structure of the protein. This structure is essential for the protein’s biological activity and stability under physiological conditions.


2. Post-translational modifi cations: Amino acids can undergo modifi cations such as glycosylation and phosphorylation, enhancing protein function and therapeutic potential.


3. Cell culture media: Amino acids are essential nutrients in the media used to grow genetically modifi ed cells. They support cell growth, protein synthesis, and overall productivity of the biopharmaceutical manufacturing process.


Non-essential AA Synthezised by the Body


Alanine


Asparagine Aspartic Acid


Conditionally Essential AA


Arginine Cysteine Glutamine


Glutamic Acid Glycine Serine


Proline Tyrosine


Precursors of Conditionally Essential AA


Glutamine / glutamate / aspartate


Methionine / serine


Glutamic acid / ammonia


Serine / choline Glutamate


Phenylalanine


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